I think that the 9XL with about an 18T pinion will do you nicely. Not too crazy on the bottom with a top to keep you ahead of the nitros. BTW, we're running a 46T Kyosho plastic spur on the 8ight. It did take some doctoring to make it fit. I had to turn the bearing standoff down by about 30/1000ths, I faced that side off by about 10/1000ths and opened up the back for the diff cup by about 20/1000th on a lathe. The whole operation only takes a couple of minutes. It's really just a matter of having the right tools.