Wait till you start planting it! When I first go my 90 I had a bunch of Amazon Swords and some Dwarf Sag to plant...so I'm standing on my stool reaching down in there, guestimating my location, and planting away happy as could be.
I step back from the tank and just laughed. All my plants were in the back 1/4 of the tank...it's so hard to judge moving from a skinny tank, lol. That and water perception is tough from above, and that's the only way to plant a 90 on a stand (if your 5'10" like me, lol, wear sleeveless shirts too).