Need advice on a setup?

The 1515/1Y on 6S is going to be too much in my opinion. More voltage is usually a better thing, but I'd get a lower kv motor to run on that much voltage. The 1515/1Y on 4S is about perfect in a truck. On 5S it gets to be a bit too much. On 6S I think that it would be way beyond practical.

My everyday setup in my 8ight T is a 1515/2.5d on 5S. Geared 18/48 with Proline Badlands MT tires, I clocked it at 50 mph. It's a lot of power and speed for a truck. For 6S, I'd get a motor with an even lower kv rating.

Since you already have the 1Y, I'd just run the 4S setup and maybe get a 5S pack later for occassional insanity. The 1Y is a good motor and the Compro stays very cool.