So I started doing a FW leak test tonight on my new 11 foot glasscages (glass) tank and filled it half way up and see that I have 1/2" difference from one end to the other. The tank is 11 foot long so not sure if I should try to shim or not. What would you guys do? 11 foot is a long span so I want to do it right. Tank volume is about 350 gallons.