I have another Kitfox IV that has slab sided tail surfaces. Call me an odd duck but I actually prefer the aesthetic looks of them over the airfoiled speedster surfaces. I'm not at all worried about cutting ribs, most of the ribs are probably intact anyway. Even though I prefer the slab side surfaces I am more than willing to keep the airfoil surfaces for a benefit. In that vein, I have been reading past Kitfox articles and found one that said:

"The vertical fin, rudder, stabilizer and elevator have a moresubstantial appearance with their newintercostal ribs and they do give the tailgroup a more effective feel in flight."

So it sounds like there is a handling qualities benefit. Be nice to hear from anyone that has flown both to see the magnitude of this benefit.