I'm at a turning point now and unsure as to whether I should stick with the road wheelset and whack on a road caliper brake on the front (fork is already drilled for it) or put the MTB wheels back on knobblys and all and put the cantilever brakes which came off the frame back on. Rear brakes are a significant challenge if I go down the 700c road wheels as the bike is fitted with chainstay mounted cantilevers and there doesn't appear to be any space for road calipers to be added.
The final thing is whether I'm dreaming by using a 50x16 ratio? The big ring isn't easily changed but i can bump the rear up to an 18 with no problems.

Appreciate anyone's advice or criticism.
