most annoying part of doing a Nomad Screen Mod is centering the new screen just right in the unit. The display on the eBay 3.5" screens are slightly bigger than the nomad stock screen so getting it centered is a bit of a hassle (plus the LCD "hole" on the nomad is slightly slanted). I found some packaging foam from somewhere and decided to make a guide template.
Using this crappy unit I have for the experiment, I cut the foam out to the exact size of the inside of the case, cut out the button and dpad holes so it would sit flush, traced the screen hole from the outside (easier since this unit is missing the screen protector), and then lastly centered the new screen with the guide in place and then traced and cut out the outline of the 3.5" display lens.
Daisy chaining some nomads together so I could run proper video while I was testing the placement of the display screen in the case.
Just the right size for the new display.
Cut out some spots for the corners of the screen for when I hotglue it in. Just did two corners for the glue to keep the screen in place, and then I'll take out the guide to keep stress-use slightly down when I glue in the other 2 corners.
...and here it is finished inside the nomad case ready for use.
I'll have to see how it holds up after multiple uses, so I may eventually remake it out of posterboard or some other material, but it'll do for now. Here are some shots on some other games so you can see the even-ness of the placement.