Bicycle Mechanics - Questions about Cannondale F5 (2007)

I bought an F5 last year, XL frame. It fits OK -- plenty of clearance over the top bar, but I wonder if it might be too long and if I'm risking injury because of that. I'm 5'11", if it matters. Is there a 'correct' or 'ideal' position of one's arms, shoulders, or head in relation to the handle bars? Is there some ideal angle between chest and triceps (when viewed from a profile)? I read somewhere that that angle should be no greater than 90 degrees (at least I think that's the angle being referred to).

Secondly, assuming I keep the bike, I'd like to make it more road-friendly. All the equipment is stock. I was looking at a Cannondale Bad-Boy and found it has the same geometry as the F5. Can I put road tires on the stock rims (Sun Black-Eye 26", 32-hole)? What's a good tire that'd fit on those?

I'm a bit of a newbie when it comes to bikes; I'd appreciate any advice even tangentially related to my questions...

I was looking at the F5 when I was bike shopping. It's a good bike. The bad boy was on my list of bikes as well, I test rode it; nice bike, the gearing is a bit different on the bad boy, more suited for street riding. But it was just out of my budget. I also test rode an 07 F4 and fell in love with the raw aluminum finish. Shortly after I bought the bike I ended up putting Specialized Nimbus 26" x 1.5" tires on the stock rims that came with the bike. It's worked out great so far.

Nice looking bike...

I got my F5 on impulse -- the matte-black frame grabbed me instantly. Sales guy at the shop had me pegged as such and said the F5 XL frame fit me fine, but it's definitely too big. I love the bike otherwise. So I'm planning to use it through winter on a trainer and switch to a road bike next year.

Thanks for the recommendation on tires, those are exactly what I'm looking for.