Glass Info for custom reef tank needed

I'm looking at building a custom tank out of glass

33 7/8w x 33 7/8l x 23"h

if i build it with 3/8 th glass will i need supports on the top? if i move
up to 1/2" if so will i still need them?

the reason i'm asking is i believe i need them with 3/8" but i would have to
put 1 in the front and back and 2 overlapping on the sides so i would
allmost lose 1 " off the tank height and they would probably look horrid, i
saw at my lfs he had a 30 x 30 x 24 with no top supports...

also how outrageous is 5 drillings? 2 for 1" drains 3x 1/2" returns in each
other corner, my planning for this is the return opposed to the overflow
would be constant and the other 2 would be off a wavemaker (flapper) thus no
powerheads in the tank

Thanks