The Distortion is an excellent pup that works well with many different magnets (like the Custom). I've personally tried the bridge Dist. with the ceramic, A8, UOA5, A5, and A2 (I probably even tried A4 but I don't remember specifically). They all sounded great, except for the ceramic (lol). The A8 kept the main character, agression, and bite, but smoothed the mids and took away the brittle aspect of the high end. From what the OP says he wants, I would suggest either the A2 or the UOA5 (my personal fav mag in the Dist is the A2). Either of these will give him the "rounder tone" he is after and will also "tame the beasties a bit", with the A2 meeting that criteria with the greatest amount of success. The A5 and A8 don't really "tame the beasties" much, but do warm up the sound a bit.
For the neck I would think that an A4 or UOA5 would fit-the-bill better than an A5.