According to that calculator, the top tube length would be ideal. I measured about 78cm from the center of my BB to the seat rails (I assume you measured to the top of the saddle), so I'm guessing I would have about the same amount of seatpost showing you do. I wouldn't cut the steer tube until I was positive I needed to.
Yes, I measured to the top of the saddle. It's 73cm to my seat rails. You'll gain about 4 cm on the steer tube, compared to my built, so with a high rise stem like
this you should be able to achieve bars level with the saddle. But you won't get much extension on it.
On the cantis: they seem to work pretty well with the fork mounted stop...but it hasn't seen many miles. Additionally, the part is not all that easy to find. I was lucky that a LBS had it for $10. Cheapest I could find online was $22 shipped from Harris Cyclery.