Getting flipped off the rear end of the bike ... you can't be serious! Just hold the hell on to the bars while leaning/ pulling yourself a little forward in the seat. If you know you are going to do a few launches and not extended riding afterward without reinflating the rear tire, drop the rear tire pressure to about 18-20 psi. Get the revs up and quickly feather the clutch out. Spinning the rear during the launch is not going to do squat for your acceleration. Crank the rear suspension up as tight as you can get it and if you want to get a little wilder you can figure a way to strap the front suspension down with ratchet straps.
Here is a video of a fairly mild launch on my Fat Bob at 4-4.5K RPM with a quick clutch feather. No reduced tire pressure or fork strapping. ....
http://www.youtube.com/watch?v=trtxe...e=channel_page

 

Tried a few launches myself at about 11:30 at night coming home from work on rural roads..got successively braver till the night the front tire came up about a foot and carried until i hit 2nd gear..scared the crap outta myself! Had thought maybe i would spin the tire..but it hooked up good...remembered to keep the front end straight when dropping back down..quite a rush!!

 

screamin 110 will you post a link to the "full sack" clip?