I don't completely free feed mine pellets, but they probably get a whole bowl a day. ....can I ask where the egg cup came from?! IMO it's ridiculous to expect a giant to live on that and be in good condition...even if they are a great hay eater. :roll:
I'm not sure what you mean by egg cup.. Guess that's the general "rule" here?
Well, I have a similair rule: 15 grams of pellets per kg (that's for adult rabbits) because I think you're absolutely right. An egg cup would certainly not be enough for say a Flemish Giant.
Then again, I think you shouldn't feed by any rules. Every rabbit is different and so are the conditions they live in. Mine get about 60 grams pellets (Science Selective), 800 grams of veggies, a bowl of dried herbs/plants/veggies and unlimited hay and grass. That's for three rabbits, about 5 kg in totall I think.. Maybe a bit more, Pip is only twelve weeks and still growing, I do feed her about 20 grams extra (she could eat more but doesn't want to) and I used to free feed her.
Now some might be shocked by the amount of veggies I give, but it's working for them. They're in perfect health, their weight is good. In fact, Pip didn't eat hay, untill she was bonded with my pair and I started feeding her the above. Sure, maybe other rabbits would get fat or underweight or stop eating hay.. But that's exactly why I think there is no "perfect" diet in general, you should look at each rabbit individually.
I think free feeding could work for some rabbits, especially if they're used to it. If you always feed your rabbits just an eggcup of pellets and then suddenly start free feeding, I can guarantee it will go wrong. They simply don't know how to keep measure.
I do think most rabbits that are free-fed, eat less hay, or no hay at all. I used to free-feed a muesli mix and they were not fat, but they didn't eat hay. Unfortunately I never managed to get Indy to eat hay, not even when reducing his pellets.. Not even when not feeding him any pellets.. So because of that, no free-feeding for me anymore!