Our daughter is very wriggly, and that appears to mean that she can eat a whole lot (we did a formula feed once at night rather than a breastfeed, and she ate 10oz formula for something like 5 hours), and we keep having to revise how much food to make for her (yesterday she had her portion of pasta, then I wasn't hungry, so she had my adult portion too), I don't suppose it could just be that you have a greedy little pig like ours and are underestimating portions?
On a related note, we are doing baby led weaning, which basically means you just give em a bit of your food and let them eat it if they want (site about it), and it works really well for us. At 7 months, she seems to eat a whole lot of some things (curry, dal and rice is the big favourite at the moment, cheese omelette is a big hit too, anything with pasta also, as long as it's shapes she can grab or long pasta). I'd totally recommend that (there is a book, which is good for being confident about it / answering questions, but really can be summed up as a)give them stuff that they can pick up, b)don't put salt in whatever you cook, probably be a bit careful with the chillies etc.) The only downside of it is that if you're not careful, she'll nick your food off your plate - because she knows how to get food, you have to keep an eye on how close you're leaving food to her (she grabbed and ate a big bit of my wife's cheesecake the other day).
Joe