I have a Perfecto 220 tank (72" L x 24" W x 30" H) & pine stand that has a Mfg sticker of 2004. I purchased it new in 2005. My stand looks similar to yours. The 3 boards that run from front to rear are what my tank sits on. No foam or shims between my tank & the stand.
The only difference I see between my tank & yours is that the bottom plastic frame of my tank also has two support pieces that run from front to rear. I don't see those two pieces on your picture. I don't know if they are missing or never existed on your tank. Can you post a pic of the bottom of your tank? Or see if they might have been broken off before you got it?
Also, when we leveled our tank, we made sure the stand wasn't too close to the wall so it wasn't sitting on the carpet tack strip that secures the carpet. We also used a shorter level & placed it on top of the stands 3 wooden support pieces from front to back to verify the stand was level. We put the tank on the stand and then measured front to back and side to side. It looked good so we filled it with water. But it was off a bit side to side so we drained it & shimmed til level. Refilled with water, only halfway, & let it sit a couple days. Everything looked good so we cut some permanent metal shims to correct thickness, drained tank, inserted shims, refilled and it has been OK since 2005.
The only other thing I would check would be the stability of the stand. Does it wiggle at all without the tank? Do all the staples seem tight? Any soft or rotting wood? We added a couple Stainless wood screws to beef up our stand a bit when it was new. Ours is stapled also but hey, I figured Perfecto designed the stand so it should be OK. Next time though, I will probably beef it up a bit.