Experience of one: my average birth weight DS put on an entire pound in either week 2 or 3. The midwife's comment was, "Whatever you're doing, keep doing it". Which was feeding him for seemingly endless hours; must have been Gold Top .
My lactation consultant insisted that it was pretty much impossible to overfeed a breastfed baby.
My daughter also grew rapidly during her first month, too. She went from ~50% to 90% within the first month or so, and she's stayed there ever since (she's quite tall for her age and normal weight for her height).
All the (bf) babies in my family have been born average, hurtled up the centiles as littlies, then slimmed back down gradually as they got mobile, ending up as average-slim adults. I'm sure super-pudgy 6mo DS will be doing the same.
So for my next question - the midwife said I can chill out wrt waking ds up to feed ( he was jaundiced so I was stressing about him getting enough milk). However, it seems he naturally wants to feed every 3 hours in the day, but will go 4 hours at night. He has both sides at every feed - about 40 mins in total - but left to his own devices he wouldn't be doing the minimum 8 feeds in every 24 hours. Should I try and feed him more often in the day to get him up to at least 8 feeds?
DS was very sleepy and jaundiced and I did need to wake him to ensure he fed, but he was losing weight. Your DS seems to be doing really well, so I would be less concerned about him going 4 hours at night.
Don't worry too much about weight in the first few weeks. IIRC, the red book doesn't have lines for the first 2-3 weeks because catch-up/down growth is so common.