I've never ridden a Mark V. I have a Rob Roy set up as a commuter (fenders and rack) with Tony's deluxe fixed wheelset. It's a very stable bike. In large part I think this is coming from the relatively long stem (120) that I am running. It's worked out very well for me banging around on rough city pavement.
If you plan on running fenders the Rob Roy is set up with V-brakes which IMO makes fender installation easier.
Since I don't know how strong you are I won't offer gearing suggestions.