add lightness everywhere, 58" by 6" looking at the pic that just doesn't look right, you can add a bit of chord without it looking wrong unless you want scale. but at that higher ratio it won't be zipping around the patch funfly style.
going with a fairly thick section should give more lift, and slow it down, giving it the right feel, but using the right gear and engine you might just get it right.

my tips... micro gear, and forget the D box, on flat section you can go to an italic D, the top spar is in the normal posistion, the lower is further forward. first benifit is less sheeting hence lower weight, i think i had shear webbs, forget now, too long ago, but the wing was super strong and didn't warp at all. any design i did now with flat bottom would inculde this feature.

think light, enjoy the build and flying, however it turns out.