Anyone use the 81T spur in their ST or SC? I'm used to an 84 in my associated but don't really want to buy a machined one for $15 just to get 84. I ran 20/87 with a 7.5 so I'll probably just try going to a 21 and see if that helps. 19/81 is right in between those two so I thought that might be a good FDR. Dropping all those teeth though I'm wondering if it will change the feel and make it feel harsh? It should however put the motor closer to the rear axles for a little better grip too.