Looks good. I had a very similar set-up when I lived in Vegas. I didn't really need the intake fan, as the exhaust fan will automatically suck-in the fresh air.

If you know what pot sizes you'll use, be sure to make the interior of the growcab compatible with 'em. (9 - 5 gallon pots will almost fit a room 36" x 36", but the more you squish 'em together, the harder it is to comfortably work with.)

Most pots I've worked with are:
5 gal. pot: 12 1/2" in diameter
3 gal. pot: 10"
2 gal. pot: 9"
1 gal pot: 6"
(All sizes approximate)

I also made a hole in the floor of the grocab to fit over the air conditioning register. Really helped during the summer out there, and I could close it (the register) as need be.