Yes, but if you gear more in an heavy vehicle, that's the ESC which will suffer a little more. The danger is that your motor temps will be colder than the 1515, so you will want to gear it up a lot...
Anyway, nothing replace the test, with checking the motor and ESC temps every minutes the first run
Inferno VE MMv3 NEU-CC 1515/1Y 4S "Flying machine"