What size kite? 10M? The smaller kites are ok to shorten the lines, but the larger models, you'll want the length so you can still loop the kite. If you can't easily loop the kite, then the line lengths are too short imo.
Sure you can replace ELC's, and just loop the lines together. Then working from the mixer, you can larkshead onto your leader lines.
For the mixer, you'll probably want A=B=C=Z (stock) for optimal turning speed. Check all lines that go through pulleys/rings, as they tend to shrink (exchange or add pigtail to bring back to stock length). Check each individual bridle lines for shrinkage and bring back to stock. Lines that are not under as much tension tend to shrink faster (B,C).
Regarding turning speed, I think the best thing you can do is get a bigger bar. The other thing that will help turning speed is a pulleybar. Lou Wainman used one on a 6M psycho3 I believe. I tried it and it works great, I'm surprised other people aren't riding flysurfers like this.
http://www.foillia.it/public/forum/inde ... -psycho-3/