CRT X1 CENTER DIFF 62t VS. 46T ???

cheesecake, i am running the 1y. @ 2200 kv, my initial was 13/62 for 38 mph, now im running 10/46 for 39 mph

ok, new problem guys...i went with the 46 center gear ....with the 1515 2.5 finned motor ,in order to use a small enough pinion ( i bought a 10,11,12,13 )to get close to 40 mph the only pinion that will fit is the 13(which will put me at about 45 mph)...if i use the 12t (optimum gear @ 41 mph )the fins of the motor will hit the rear center brace...so ...to you guys running the CRT X1 using the small spur gear ...are you grinding down the center brace ??...or just running 13 or larger pinions ?? thanks ,i hope this makes sense ...lol...cause now i'm confused....thanks again for helping a noob out
....this will be mainly just for the track ,so i'm aiming for about 35 to 40 mph....is this about right for a truggy ??