Most the info for what you are looking for is here:
http://www.paulcbuff-techforum.com/viewtopic.php?f=8&t=1409You are looking for Hypersync and not High Speed Sync... easy to get confused but drastically different. Studio strobe don't do HSS because it's a strobiscopic type of effect. Hypersync optimized the burn off of a single flash.
More here:
http://www.paulcbuff-techforum.com/viewtopic.php?f=8&t=1580&start=10Read especially in the last line where I mention a small bug I found in my Flexes that require me to set the high speed sync crossover from Auto to a number (IE: 1/640) click apply and then set back to auto. I have been syncing at 1/8000 of a second at ISO 200 at 10 feet ever since. With the 5dMKII sensor though you might only get that at 1/4000 though. Getting one in the studio to test on soon.