Hey guys,
I'm new to this forum, but I've have already gotten a ton of good ideas from here. Let me throw one in myself.
If you are a pretty good fabricator, you can try this. The easiest and cheapest way to stretch your swingarm is to cut it off between the main body of the arm and the plates that hold your carrier. You cut it straight from top to bottom right in front of the carrier. Weld in a spacer of whatever length you want (mine is 2 in.) made from 3/16 steel (or 1/4 in.) on both sides. Then, weld a brace running between the two spacers for strength. You can use angle for the brace if you want, but I just used a piece cut from the same stock as my spacers. It is quite strong and you don't have to worry about your shock linkage like you would if you tried to stretch the body of the arm. You do have to use a 104 link chain and you have to disconnect your parking brake cable, but the brake line is long enough (just barely). You also have to tighten up your preload on the shock because of the extra leverage. I hope this helps.
As far as the reason to do this, it helps me keep the front down when climbing or drag-racing. I know not everyone agrees, but that is my reason.