I'd load a test pattern in spaghetti and adjust until it maxes out the galvos, then measure the width of the scan at the approximate position that the aperture will be. That way you can make sure the aperture is large enough to allow full-range scan motion without cutting any of it out. So really, it depends on your scan angle. I'd make it as large as possible to allow for larger angles in the future. In the case of my current scanner project, I'll be making the entire front of the scanner out of pexiglas. It's overkill, but I'm guaranteed to be able to use any scan angle.
the dimensions are 7.5" x 16.3" x 17.5" (W x H x D)
I couldn't find the dimensions of the scanner parts but I'm hoping they aren't too crazy big, anyone know the height of the scanner op amp boards? they look to be the biggest part.
Instead of that laser I'd go ahead and spend the extra money for this one. It does cost about twice as much, but it's WAY higher quality. I just bought one and it's awesome. 150-175mW all day long with rock solid stability (mine takes about 5 minutes to warm up to full power and stability)..
i honestly dont like computer cases for the enclosure. but it is all personal preference.
you want something that will have a very sturdy place for the lasers dichros and scanners to mount to.
otherwise you will have to deal with things getting out of alingment and you constantly having to adjust the dichros and mirror mounts.
i have seen some people use horizontal pc cases very successfully but they also used a thick aluminum plate as the base plate.
the scanpro 20 amps are VERY small. heres a picture of my micro 500mw green build.
the scanner amps are in the top left hand of the enclosure and the size of the entire enclosure is 10"x6"x3.5"
here is another picture of the scanners sideways
as you can see they probably go half way across when mounted side by side so thats about 3 inches but something that isnt shown in those pictures is the way i mounted them, scanner amps are prone to getting very warm-hot and you want them as cool as possible, i have mine mounted to a nice thick piece of aluminum to help them cool.
you will want to do the same, but most likely you will have a thick baseplate you can mount the the amps to so that isnt a problem most people have.
it has a 500mw green laser wave module that is self cooling and does not need to be mounted on a base plate at all. the laser driver is also self cooling and has two fans on the bottom of the heatsink. and the scanner amps are mounted to a piece of aluminum. the psu's are mounted in a way where the fans circulate ari through them using my fans inside the laser.
this picture describes airflow.
the lasers fan and the drivers 2 fans pushes air out the filter on the left, and then there is a another matching filter on the opposite side that you cannot see that lets airflow in and then there is a fan and filter on the top that pulls the air through. all of the parts say cool to the touch.
it is completely sealed besides the filters so i can use it in dusty settings with no worry of my optics getting dirt on them