If you're thinking about a 'bent, I'd definitely run it by your doctor first. You can't use your arms and legs as suspension like you do on an upright bike - meaning all the road shocks are transmitted through your spine - and it's exacerbated by the fact that they can't see the road well enough to avoid potholes and rough spots. 'Bent riders I know are pretty miserable on less-than-perfect roads.

As far as being seen, when I'm in the hooks but not a deep tuck on my Synapse, my head is level with my friend's on his Bachetta. I think the main difference as far as conspicuity is on an upright bike you use your clothes, on a 'bent you have to use the seat and/or any luggage.

Something to think about though.