Quick motor question

Ok, so I might be building up a revo. Would be for the track, thats all the details I give

I need to make 15-20 min run times, and have a mandatory batt swap. Thats the rules

I want to go light, but dont want to be pushing runtime, 15 mins is max I can go till I have to swap batts, So a little longer then 15 is good

Heres the question, for racing, I dont need power, I just want to run 5, or 6s to be efficient, I dont want crazy power though, needs to be controllable. So im looking at running a NEU 1515 2.5D for 5s, 1.5Y for 6s

Any comments on this? I dont want crazy power, just want runtime. What batts should I run? What motor should I run?