I couldn't disagree more. The 5kg weight rule dates back to the 1930,s and has for some reason has never been changed. It does nothing to limit powerplants as we've seen engines go from a max 10cc displacement to no limits at present. We have more power with glow and electric than ever, probably more than needed so the rule has had no impact on powerplants. At this time it serves no value because there is only one contest in the US where airplanes are checked. If it had a value we'd check planes at all contest.
The way the rule is applied to electrics and glow is grossly unfair to electric power. Most Glow planes take off at well above the 5kg limit with a full tank of fuel.
The other thing it does is drive up the cost of our planes trying to meet the 5kg max. Expensive carbon fiber parts, expensive construction techniques, expensive lightweight radio equipment, props, landing gear, etc. And a heavy airplane never flys as well as a light one even in the wind IMO.
The USA should show some leadership in this issue by eliminating the 5kg rule in AMA classes and perhaps FAI would see fit to change also.
Give me a minute to get my flame suit on!
Dave