RC8 Brushless Discussion

sorry to bump an old thread, but am hoping you guys can confirm something for me... I could have started a new one, but figured this was totally relevant, and there was not much point...

I have an RC8 with the tekno conversion, and am running 4S 8000 20c packs (2x 2S) with a Tekin RX8/T8 2650kv motor - i cannot get past 10 minutes without it thermalling on me - geared 16/46...

I was considering going to 3S, but figured it'd be cheaper to just change the motor out, so am about to get my hands on a Tekno Neu 1512/2.5D/F (5mm shaft, 78A, 2050kv, blue) and run that on the 4S packs...

I am wondering what kind of runtime you guys are getting?? I need to make 30 minute mains locally here, and am brand new to the buggies and racing...

I'm also curious to know if running a BEC will help with heat and/or runtime at all? Cheers guys =)