I like to focus my G2 at 15 feet and set the 6X pair about 30mm apart and about 15mm from the G2.
Your 12mm heat sink hole has to be perfectly perpendicular to the heat sink face and your beam square to the heat sink face or you will need to adjust tilt as well as some slight rotation of the cyl pair, I like to set each lens by hand with it hot/lasing, safety glasses of course are a must.
With a DTR G2 my 44's beam runs from 5mm wide at exit negative divergence to about 6 feet and then positive back to 5mm wide at 12 feet, by 32 feet it is 15mm wide.
Without the 6X pair my 44's line through a G2 is 50mm wide at 15 feet.
Here is my pair set up and working well, the on pic (blue) is with a DTR G2 and the off pic is with a sanwu G2.
The sanwu G2 (Bottom pic) is 31mm apart center to center for the 6X pair. If you look at the space between the aluminum blocks the DTR G2 looks like 35mm between the 6X pair.
The sanwu set up works with his 3X expander, but the DTR G2 would truncate in the expander, also I set closer with the Sanwu, but it does not run negative then positive.
Here are a couple videos of the SANWU G2 vs DTR G2, there is a FL difference as the sanwu will not run negative then positive even benchtop, but it works with his 3X expander.
It seems the DTR G2 is cleaner and better for 6X pair use only, but if you want to use the 3X after 6X correction, and it really works! I needed to use the sanwu G2 to make it fit inside the expander.
I could be doing it all wrong, but this was my experience, sorry for the long answer, I hope it helps.
So please correct me if I am wrong, but you mean that in order to fit the 6x expanded beam from 44 into Sanwu expander I will need to replace DTR G2 collimators (30 dollars each) with the cheaper Sanwu G2 (15 dollars each)?
And the cheaper ones will work better for this set.
With the DTR G2 and 6X pair I got a nice beam correction, a much more useful ribbon of blue.
But if adding in the 3X expander you are correct, with the NUBM44 I could not get the beam to work after 6X correction with the DTR G2 in the sanwu 3X expander, it would not fit the expander no matter how much I tried it was clipping the hell out of it, however it works like a champ with the sanwu G2.
I could have overlooked something, but the lenses have a different FL.
The input lens of the expander was blowing up the DTR G2 output where I could only get about 1/4 of the beam through, I suppose I could defocus it, but setting the G2's focus to 15 feet and then infinity it would not fit the expander either way, maybe if I defocused it but that woud be counter productive.
The videos demonstrate how the focal length of the G2's is different, I believe sanwu's G2 has the shorter needed focal length.
Notice how I set my 6X concave very close to the tight output.
The videos use a NUBM06 that is less divergent by 25% but that matters not, the principal is the same.
More testing is needed but I could not get the DTR G2 to work with the expander after 6X fast axis correction, now if you use just the G2 and expander that will work, but not near as well as with the 6X in the train.
I would use the sanwu G2 if going with the 6X and 3X expander, but experiment if you like, see what you can do, I can burn cardboard at 75 feet and that's no small task for the ultra divergent 44 diode.
Yes, it's possible to build a compact corrected nubm44, but the duty cycle would have to be short. It is something I would like to do, I really want to see a 5w green diode, how have your 520's been for longevity?
I have never had a problem with my NDG7475T green running at 1.4 watts output, I don't see reports of failures coming in for those like I have for the NUBM07E 465nm baby blue being pushed at 4.5 watts out or more.
I have used the 6X pair with the NUNM06 and NUBM07 with DTR's G2 and that works fine, but I have not used either with the 3X expander and 6X pair. The 07 is pretty but down on power compared to the mighty 44. The 44 is also tougher in my opinion, much tougher.
However the 07 is a little less divergent than the NUBM44 as is the 06 so it should work fine with a sanwu G2 and 6X pair plus the 3X expander, the 3X expander may work with the 6X and DTR G2 as the 07's divergence is less so the beam width will be less, it was with the NUBM06. The beam diameter was under a 1/4 inch from 0 to 15 feet with the NUBM06 and 6X pair.
Here's the 06 with a DTR G2 and 6X pair, the NUBM44 is stronger but the beam is wider.
In the video I say 1/4 by 1/4 but I meant to say under a 1/4 inch, you can see how the DTR G2 runs negative divergence then positive, it's really tight half way, that's with the G2 focused at 15 feet, at infinity it moves out but still was too wide with the 44 for the 3X, but sanwu's G2 was a narrower beam, albeit less clean at the splash as you can see in the 2nd video.
Here is the NUBM44 with a sanwu G2 and 6X pair plus a sanwu 3X expander, this burns through cardboard all the way across my backyard @ 75 feet.
You have written that NUBM07E with Gball makes a 25x50mm box at 15feet similar to what NUBM08 produces. Are you sure?
In this blaster I have combined one 07E with Gball and one 07E with DTR G-2 and both lines before expanding looked similar when I aligned them (of course I did it at 0.3A current, not at 4.5A). But now at 4.5A ~10x expanded beam does not look too bad due to one LD with Gball: it forms ~1cm round spot at 5m (what should be 15 feet), then diverges horizontally again at 50m into a ~50x20mm box.
This means I did not collimate it well - just focused at 5m distance by choosing right separation of cylindricals.
0.3 Amps will only give you some of the dominate center wavelength, the side bars won't even come in, try it at 3.5 amps or more, you can do it with just the raw output and see the side bars light up as current is increased.
I made that mistake before measuring the spot size at half power and it was much smaller, but turn up the current and watch it grow. LOL, yea I know, that's what she said. But seriously at 0.3 amps you will get a much narrower output with a multi mode diode.
I am looking for a video I have, but you can do it with any multi mode diode, shine the raw diode output on the wall and slowly turn up the power, you will see the center bar then the side bars come in as the power is turned up.
These are NUBM07 pics, you can see the Gball is on and you can see how wide the beam is at the 15 foot end, but just turn up your current and you will see it grow.