Need help with DIY tank stand!

[LexUnit]

I'm building a DIY tank stand using 2X4s. Just made the to base that a 40 Gallon Breeder tank will sit on. I see small gaps around the Plastic trim of the tank (where tank meets wood). My friend says the tank will flex when filled and the gap will go away. I know that you have to level tank and stand with shims to prevent leaks. This is my first Stand build. So any help would be great.

Thanks

 

[solo]

A piece of plywood on top could help fill the gaps or a sheet of styrofoam