1350kv, assuming 6s so 22.2v nominal, 16/181 gearing,.. the math shows 2649 possible. I'd agree with chris,.. wouldn't go much lower. If you check esc temps at end of each flight you may be able to get it down a little more that Chris states but I'd be very careful on esc temps. ESC temp will be the critical thing. KV and gearing is really too high to slow it down much.
I'm doing 2100 and 1700 but using an 1100kv motor with 16 tooth pinion.