ORIGINAL: nonstoprc
It will be a huge discontinuity between AMA and FAI if the same weight limit is removed. If somebody ever wanted to move to F3A, he has to assure his planes are under 5000grams. Worse, he has to regain/retrain the skill set for flying a lighter plane.
Not really, eventually FAI will eliminate the weight rule too if it's counter productive and there is a demand to change.
And a prosapective FAI flyer always has the option of flying a less than 5Kg plane. As a matter of fact top AMA flyers in all classes will want to fly the lightest planes possible weighing the cost/benfits of doing so. But removing the 5Kg requirement at least allows others to compete for less cost if they choose.