Sorry - A.D.D. -- didn't realize you said MID 20's in the prior statement.
When I had the 33x10.5's mounted on 15x8 cragars I did run them lower. About 30psi in the front and 26.5 in the rear just to flatten the patch. Summertime I run around without the back seat, instatrunk thingy, and keep the back 3 windows out while tucking up the rear of the soft top on top of the roll bars. For about 3-4 months in the winter I run with everything possible in the back to put more weight in the rear.
Reminds me-- I need to mount the hi lift on the instatrunk thingy.