If you are just using the Walker for casual shooting you could keep that small nipple as the "open" chamber where you let the hammer rest. Otherwise I would make it the first chamber to be fired. That way, even if the cap is a little loose it is not likely to fall off if pinched. If it is not fired first and capped, the recoil could cause the cap to fall off. If it is the first to fire then no problem and the rest will stay on anyway.
With over 15 perCUSSIN' revolvers, I've been called the Imelda Marcos of cap & ball.
SASS#3302 (Life), SASS Regulator, NRA (Life), DGB#129
Wolverton Mtn. Peacekeepers (WA), former Orygun Cowboy (Ranger, Posse from Hell)