I am running 6 valves on my truck, the front is individual ,and the back is T'd together. I've got no problems with body lean at all and I drive my truck probably more than most people do. The only thing I wish I would have done different is run 1/4 " air line, 3/8 is too fast for me. As for putting guages in the cluster I think thats a good idea, that's what I did with mine , and it works well. I'm also running silencers on my system ,and would recommend using them, they quiet it down quite a bit. I think they slow the dump down a little too. As for cups or plates , I think the cups will sit a bit lower than the plates,( after you cut them down) but the bag may touch the smooth, rolled edge of the LCA when at full dump (mine does). The plate system doesn't let the bag touch anything. I personally used the cups. Hope this helps.
.......Oh yeah ,I couldn't resist not painting my truck. It's in the process of being painted right now. I'll probably regret it later on. Oh well.