If you want 2" lip it would be 40" not 38"
I usually advise solid framing landing directly under the vertical glass panels, usually if a 2x4 frame then I make it land in middle, and that bumps 3/4" outside it, and then frame skin another 3/4" and that makes 1.5. You could cheat that out some to make 2"
If it's a non trimmed/rimless tank usually the bottom glass panel needs full support, so solid joists across middle, and I usually advise 3/4" ply on top to help ride over any deviations.
There's a fine line between owning your tank, and having your tank own you!_________________________________________
120G SCA starfire, tunze 1073.02 return pump, Geisemann reflexx 4xT5, 2x panorama pro LED strips, 2x Vortech MP 20's, 40g sump w/ fuge.