Is the bottom of the tank a flat piece of glass all the way across to the edges...
Or does the perimeter of the tank sit some distance lower than the flat bottom?
Manufactured acrylic tanks typically have flat bottoms with no plastic trim. This allows the weight of the tank/water to be evenly distributed across the full surface of the bottom of the tank...
Manufactured glass tanks typically have a plastic trim going around the perimeter of the tank. This allows the weight of the tank/water to be carried only by the supports below the perimter...
If your tank is supported by the perimeter, you would be best off having the full perimeter supported. I've had such tanks with a couple inches on the ends overhanging a stand (as if you were to use a 30" long stand)... but I would not do so with the front/back overhanging the stand (as if you were to use a 12" wide [front to back] stand)...
If the tank has a flat bottom with no perimeter trim... I would then be comfortable using a stand meant for a 3' x 1' tank and allowing the front and/or rear hang over a bit...
Although personally, I would put a piece of plywood between the tank and stand...