the dons 6k works well for me in the screamer. but u are correct , the last few mph cost at the amp pump
i am able to use a 1600 40 c 3 cell and get right at 100mph. flight times are ok at 3 min but thats w/ short wfo bursts. used like this the battery gets warm , not hot.
some real battery abuse can be had by running it on 4's but it has to be brutal current wise at 50 amps on the smaller cells.