One of the problems I have on my Delta SA180 is getting a convex edge that can be completely touched up with one pass - I have to make about three passes with each grit and blend the passes with one another. I'm guessing I don't take off enough metal on the back portion of the edge and am not using enough pressure. I'm wary of using too much pressure and rounding the edge however. I really need a tutor <img src="/ubbthreads/images/graemlins/smile.gif" alt="" /> Alternatively, some good vids of your techniques (which really show how much belt deflection you should be getting to get cetain results) would be helpful.
I don't know where along the belt you usually hold the knife, but try doing it about three inches below the top pulley, and don't be afraid to put a little pressure into the belt. Just be sure to keep the blade moving, don't stop and stay in one place. Try to make your passes in one fluid motion.
Also, as Horn Dog said, try just using a good strop with proper technique to keep your edges in good shape. If they get a little beyond the strop being able to bring them back, I think the 15 micron belt is a good one for resharpening for once you have your profile like you want it.
Always remember the blade is going to heat up faster with the finer grit belts than it is with the coarser ones, so keep that blade moving and don't make a bunch of passes without dipping it in the water <img src="/ubbthreads/images/graemlins/grin.gif" alt="" />. Do not wait until it is HOT before giving it a dunk.
