This will be a cool project if it takes off. But if you were truely capable of this build, you would be able to answer some of these questions. Start dwelling around on the RZ/RD forums, they will be a goldmine of info for stuff like this.
The shorter you go the easier it is to turn and get traction. I don't often jump very big, but with forward A arms and negative swinger, the bike seems easier to launch more balanced in the air.
Pretty sure they had a sport model. Can't get their site to pop up, and fuck Facebook advertising. It's ridiculous to just scroll and scroll, then scroll, and keep scrolling. Or search, and repeat the same process.