1515, 2.5d all the way, it,s a beast on 6s.
But be very carefull with you MGM 16018, it,s more a 5s controller than a 6s.
It,s rate for 18 eclls NiMh, so 21.6 volts, and a fully charge 6s lipo is 25.2 volts.

I
The new 16025 Z serie seam to be rated higher on voltage.

Good luck.