I know who you're thinking about, that's 05boostedes2 or something along those lines. I believe cjtech has a 2010 Si IIRC, and if so you can definitely do the swap of the cmc's. I have to do mine soon. You should really get the real Honda EM1 cmc as already recommended, as the internals are metal.
As for grinding, what tranny fluid are you running? Did you get your synchros changed as per the TSB for 06-11? Lets dig into your tranny setup and get you shifting smooth