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.