+1 to both of Matt Trimmings replies. As far as the setting of the slipper goes, I have found the same thing you have. Doesn't really matter how much motor I have, I can't get the front tires to come off the ground with an SC10. They do start to get real light though. I think that is what you are looking for in this case. Or you can just set it on the track. Its probably the best method anyway. Set it so it slips just a titch on the track and that you can clear the jumps you need to.