Their are a few different ways to build a stand ie timber or steel with or without hooding.
is it for the 55 or 120 as you will need to consider what you will be keeping under it also.
A flat top surface is important some lay a sheet of timber some go with just the frame to support the tank.
As for foam or rubber under the tank some will say yes, some will say no. Personaly I use it and it doesnt matter what anyone can say to me to change my train of thought

30 years with 48'' tanks in house never had a problem.
But then theirs others the oposite to me.
Maybee you an check some DIY sites theres heaps out their .
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55gl skimmerless, 80lbs live rock,
DIY wavemaker running 3x MJ1200 with hydor deflector.
2 DIY fluidized reactors Carbon & ROWAphos
LIghts- 2x 50/50 atinics T10's , 2x life gro T10's ,
1x20,000K T12, 1x6,000K T10.
Fish-3
Coral-13.