My Fat Boy Lo is pretty low, and it's going to get lower
Can't speak for the J & S, but the fully collapsed height on my Pit is
4 5/16ths, which is perfect on my stock height 09 Ultra. The platform just barely slides under the frame with the bike on level ground and on the jiffy. To be perfectly honest, I think if the bike was lowered, I'd probably have to use a couple of pieces of ply under the wheels.
Great information here folks... thanks to all for their input. I went ahead and ordered off for the J&S with oil pan set up. I looked at the Sears models, and quite honestly, they didn't look very well made. Based on the comments here, I highly doubt that you could go wrong with either the J&S or Pitbull setups.