Nice
I'm sort of 'with' the guy calling out the OSB... I just don't have any faith in it. It would appear that your stand structure is plenty solid enough, but even high humidity can cause OSB to expand and warp. Don't get me wrong, it'll likely be just fine... heck, most of the commercial stands you buy are at least partly constructed with OSB or particle board. My stand structure is steel, but the top is 3/4" oak plywood, with 2 coats of marine epoxy, and a 1/4" thick coat of two part bar epoxy over the exposed surface. Ok, so maybe I went overboard a bit... but I _know_ it's going to hold up
How far is your peninsula from the back wall? Hard to see in the photos, but it doesn't look like they're much room on that side. I have a peninsula as well, I left 30" behind the stand... 40 " from the tank itself (I have a 10" shelf surrounding the tank), and sometimes I wish I'd come out a bit further. Too late now... my design would _not_ allow for an easy move. I may end up building a sort of narrow 'bench' back there, lift top for storage, padded seat... Not sure yet, we'll see what I end up with.
Looks like your T5 is a bit shorter than the tank... I did the same thing, a 4' light over a 5' tank, though I think my tank may be a bit wider than yours. I looked at 60" lights, but the BRS160 (5' light over 6' tank) made me look at a bit shorter light. Saved a few bucks, anyway. The 8 bulb T5 is _plenty_ of light, for whatever you might want to grow.
Flow is a challenge in long peninsula tanks. I tried every which way to avoid it, but ended up with a wave pump on the outside end of the tank. I just couldn't find a way to get the flow I wanted without it.
Keep up the build thread... I'm looking forward to seeing what you do with it all!