I've been out for a few 'spirited' rides on 'Hilda, 60 km yesterday and 52 today, and I've been playing with the boom length a tad., extending it slightly. Now my knees are sore, across the tops, and my calfs ache a little bit, but not my thighs. Is my boom too far out? On an upwrong sore knees means saddle too low, too big a gear, but googling (bentrider online etc) they seem to suggest the opposite, i.e. soreacross the tops, boom too long. I have been trying to go faster, but also very aware of trying to keep spinning. I've done the heel on pedal thing, but that's only a starting point. Web suggests 75-90 % leg extension. I know it's a case of what works best , but.. I'm 6'2" and using 170mm cranks. Thoughts please.