he sounds a lot like my DS as well - he fed on demand round the clock & was around 90-95% on the growth charts. he was still pretty big when he started crawling but between probably 8 months (after he started crawling) & 12 months (when he started walking) he really dropped alot of the extra weight & at 2.5 looks fairly lean. he's still above 50% on the growth charts but nowhere near the top end any more - he's sort of stretched out. not that i put heaps of emphasis on the growth charts, it's just as an example.

i figured that he was stocking up because he is such an active little boy that he needed the extra weight to cope with both growth & activity. no basis to this, just my guess!

i don't think it hindered his ability to crawl, sit or walk - i can't remember when he sat but he was crawling before 8 months & walked 2 weeks after he turned 1. there's a pic of him in my photo album when he was about 6 months.