I'm about the same size as you, but I went for the 56cm frame which was sold as a 'medium'. 54cm was listed as small and I wouldn't describe 5'10" as small. Not done more than about 15 miles in one trip (or maybe 25 miles in a day) on it though as I use it for commuting. Not had any real problems - it's never going to be as comfy as my other bike with custom geometry so there's a chance I tend to ignore minor stuff. I've flipped the stem too and it seems fine to me. You're welcome to try it and compare frame sizes - I believe you're local to me as you mentioned somewhere in another post that your lbs was Two Wheels Good in Crouch End (a place I swore never to return to!).
Pushing your saddle all the way back will stretch you out and likely add to the pressure on your wrists. I've been told to do pilates to strengthen my core to keep the weight off the hands. I fractured my spine earlier in the year though so I've got an excuse to do pilates and still be heterosexual ;-)
I'm about the same size as you, but I went for the 56cm frame which was sold as a 'medium'. 54cm was listed as small and I wouldn't describe 5'10" as small. Not done more than about 15 miles in one trip (or maybe 25 miles in a day) on it though as I use it for commuting. Not had any real problems - it's never going to be as comfy as my other bike with custom geometry so there's a chance I tend to ignore minor stuff. I've flipped the stem too and it seems fine to me. You're welcome to try it and compare frame sizes - I believe you're local to me as you mentioned somewhere in another post that your lbs was Two Wheels Good in Crouch End (a place I swore never to return to!).
Pushing your saddle all the way back will stretch you out and likely add to the pressure on your wrists. I've been told to do pilates to strengthen my core to keep the weight off the hands. I fractured my spine earlier in the year though so I've got an excuse to do pilates and still be heterosexual ;-)