thats a veg and clone cupboard surley? strip cfls in the top bit, that 125w to veg as you have it....
just 1 thing mylar is useless unless its 100% flat (no crinkels at all) this is the disadvantage of using it, that and it not only reflects light but heat back in as well.
you could A use thin card to make "walls" that fit snug inside, before inserting said walls wrap them in mylar so its flat....think mylar pannels then glue in place...OR painting it DIAMOND white in a MATT finish could be an alternative...as it refelcts nearly as much light but no were near the same heat....by painting it white you can also clear it out and it would not look odd if stealth is key...try explaining sliver walled cupboards!!
just a couple suggestions! other then that well done n happy growing!