There have been a number of families of airfoils that were symmetrical profile. They were often ranges from very thin to very fat. From one to it's next closest kin, there was almost nothing of significance between the two.

What you're wondering about has been sorted out by control line aerobatics designers back when that was a major discipline. Noone really had proof there was any difference.

What you're suggesting, thinning fore and aft, actually results in a modification that moves the thickness of the profile aft. There have been lots of C/L models based on those kind of airfoils, and nothing really stood out.

BTW, the best way to do that job is to thin the ribs where they will be cap stripped a touch less than the thickness of the strips. Then you don't change the profile at all.

A lot of us "upgraded" a bunch of our C/L kits with cap strips back in those days. We always thought we had better flying planes than everyone else.....