These are the shims you need to add to the rossi XR for 30% (ontop of the one thats in there already), all you need to add is 1 of these: http://www.amainhobbies.com/product_...oducts_id/3084

They are shimmed for up to 25% and for about the first 6 months I thought it wouldnt be that big of a deal running 30% and a cold or medium plug like I normally would with any .26+ and 30%. But I ended up adding the head shim eventually, and it was a night and day difference as far as consistency tuning it. Some people say to add the head shim even if you are only running 20%, which I think is a decent idea, but I would suggest trying some different plugs to see what works best. Head clearance for a turbo plug engine should be at .024" (if I am remembering right), and thats exactly what the aluminum and copper shim end up giving you.

I love the XR, but the next .28+ for me is going to be the RB 928 when I get around to building another MT.