Um… thanks, but I’ll pass. I can’t imagine trying to ride with a brace.
Can you spell multiple UPD’s? 
Just riding around, I think the balance is with your (my) legs.
I, too, have had “core” comments but I don’t feel any core muscle strain. Maybe Grandmaster 2T’s admonition to “relax” has worked.
ahaha i’ve had “that must be good for your abs” which i think is wot good for ur core means… but american trendy words are not really my thing lol
i got that comment a few times, but honestly have no idea wether its good for me or not. Who cares really its fun 
heres a thing about your “core” from a bicycling magazine for workouts for your “core”
http://www.bicycling.com/article/1,6610,s1-4-20-15681-1,00.html
heres another and i guess its got stuff that relates to the “core” area of your body…
http://www.bicycling.com/article/0,6610,s1-4-20-1052-1,00.html
I do hear this occationally but nowhere near as often as “Where’s the other wheel!” About a 10:1 ratio
When I was learning after practicing for an hour it felt like I had done 500 crunches (which I have done before over an hours time). Also after my first muni ride my obliques were sore.
I have noticed benefits from doing extra core strengthening exersises. When I’ve been doing my half hour routine, I can ride faster, smoother over rough terrain for longer with fewer and safer UPD’s.
He said at speed (fast). Sure at slow speed or tecknical terrain it would be tough.