We recently set-up our 55 gal. acrylic w/ 70 #'s LR.
We placed a 5/8 piece of polystyrene, cut to the dimensions of the tank,
underneath to distribute the weight. Our knee wall top has a slight bow
(about 1/16-1/8") from end to end of tank.
Problem is one corner of the tank rest slightly above the pad. You can slide
a sheet of paper underneath about 6-8" square and deep under one corner.
There is no noticeable compression of the pad, but you can feel a little
tighter pressure into the side of the pad in the center. There is slightly
noticeable difference in the waterline space (waterline to top of tank) on
the end with the space between pad and tank.
Question:

Can our tank tolerate the strain in areas where the P'styrene is not
adequately compressing or making contact with the tank? How strong is the
tank for unbalanced seating?

I will be inserting a long wide wedge into the space today to try to
equalize the support on the low side, but other areas of inconsistent
support may still exist.

Any suggestions?