Otophile,
I will tell you the high output starter from Harley with a Harley Battery is what S&S recommends. 3 years ago when I had gotten a new motor after the first one lost a wristpin keeper and imploded I had the bike at Carl's Speed Shop to have the new motor put in. Carl's wanted to use a spike starter and X brand of battery.
The bike would not start no matter what they tried. At the time it was a bike week and the S&S reps were there on site for the event and working out of Carl's shop. They told me to go buy a harley starter and harley battery Carl said they were crazy at the time, and they discussed it

in the end I went and bought the stuff. Upon installation the bike turned over and started and ran ever since. The reason they gave was it was not torque that was need, but speed and that I should not deviate from this, because it works.
In the recent months time I had a heavier ring gear put on the clutch basket and a new pinion and all has worked out. There was nothing wrong with what I had this was a precaution since the tranny was being replaced by baker and was recommended to me by Cycle-Rama when they replaced the tranny.
The problem with the new bikes 07 with the new gearing setup is that there is no updates available yet to do this on them, and some of the manufactures are saying they probably wont develop anything for it. Kind of scary.