The autumn 07 Rabbiting On said this from one of its vets:
* a rabbit's diet should be 70% hay, 28% veg and 2% pellets
* one tablespoon of pellets max per day for rabbits under 3.5kg and two max for rabbits over 3.5kg.
I'm not sure about the % thing because I dont think it would stack up if you did it by weight. Maybe % by volume would work better. But the basic principle is a pyramid with a SMALL amount of pellets on top, then SOME veg, then lots of hay.
Muppet has Science Selective too - I did weigh out a tablespoon's worth and it was about 15g. SS, as well as being extruded, is high fibre which is another thing to look out for in a rabbit food.
If you were feeding only hay and veg (no pellets), then I believe it's a pile of veg about the same size as the rabbit.
What Muppet actually gets (he weighs about 3lb or 1.7kg) is 10g of SS and a bowlful of veg morning and evening. This seems to work out OK for him, his weight is stable and his poo is healthy
And he eats timothy hay like he's been starved!