You have a TC4 that you're running VTA on carpet with a front one-way? I think that I would start with putting ANYTHING in the front and see how you like it (assuming, of course, that you haven't driven it with a spool or diff in the front before). In my experience, I could be MUCH more ham-fisted with spool in the front. I had a hard time developing the finesse needed to drive with a one-way. (your results may vary).