Although not quite 50 (within spitting distance, though) I thought that this would be an appropriate forum for my query.

A lifetime runner, I took up biking about a year ago to try and lessen the pounding and jarring on my ever aging joints. After a week or two of craigs list lurking I bought the following:



My criteria: Price, fit, carbon fork, and its italian = cool.

I am now happily riding 25 miles once or twice a weekend and thinking of a century or maybe a charity ride. I seem to be able to maintain about 16-17 mph, solo, so maybe I'll try some group rides. The problem is that after 15 miles or so my hand goes numb and I have to take it off and shake it every 15 mins or so. I dont know if its road noise or riding position. LBS says the bike fit is good, when queried about possibly raising the handle bars a bit (less weight on wrist, I thought, also might help lower back) they said not possible (well without new fork, I guess.)

So my question(s):
1) Am I doing myself damage? Should I "Just suck it up and shake your hand every 15 mins, ya' wimp."
2) Would larger tires help? Say ditch the current 23 for 28 (will they fit on Aksium Race rims?)
3) Should I really think about getting a bike with more relaxed geometry? If so just buy a frame (like Scott CR-1) and use the components off this bike (dura-ace, shimano ultra) or sell this one and buy another used?
4) I read somewhere that handlebars down/ass up provides more power from quads an hamstrings (along with obvious areo advantages), true or just an excuse for masochism?