need help selecting motor for rc8

[kevin23]

well a little update,
I came across an 8ight really cheap and I had one of the tekno kits in stock at the store,so I converted the buggy using the neu.
I love this thing,geared with a 13 pinion it is really fast,a little to fast for the track,turned endpoint down to 75% with a 5s tp 25c 5000 pack.
I get 20min's runtime with temps for the motor 150-160,esc110-120,batt temps were 110-120.
Should I be concerned with the batt temps?cutoff is 16v.
I tried it on one of my 4s 25c tp 5000 batteries,had to turn endpoints back up to 100%,runtime was still 20min's same temps same gearing,was noticibly slower,but was manageable.

Should I get more runtime than I am?Would I get more runtime running 5s with 75% throttle or 4s 100% same gearing for both setups?
mm is setup lowest timing,low start power,50% punch control,12.4v for 4s 16v for 5s cutoff's
Thanks for any info,I will be posting pics as soon as I find my cable to transfer pics.

I run the 1515 2d 2050kv on 4s in my rc8...I was going to use the 1512 but mike wanted me to go with the bigger motor to help balance the chassis and offset the weight of that battery...it's what he runs in his buggies.

I forgot to mention mike also wanted me to use the larger stronger 1515 at a lower rpm to make gearing easy. because a 16 tooth pinion is the smallest you can use.