There has never been a 20% deviation from scale. 10% has been and is the rule since I've been flying IMAC (10+ years).
Hi Dave:
I guess I could be wrong, but I thought there was a time in the mid to late 90's when the fuselage could deviate by 20% from the wingspan, where the wingspan set the % scale for the model. I remember that there were some designs like the 37% Godfrey Extra and and one of the Aeroworks Extra designs that were really stretched to the max. There was a change in % deviation that tightened up the specs, but I don't remember all the specifics anymore. Remember at one time too, there were designs like the Gator Giles And Hanson's Excess (An Extra 300 that pushed the rules to the max)? If I recall correctly, they would not meet today's rules, since something did change to reduce the deviation in the fuselage scale. Was it width or length deviation that changed?