4d and/or 6d upgrade

I have both a 4d mag and a 6d mag. I am currently running the 6d mag with a 5d magnum star bulb with 6 duraloops in a 6 d adapters. Would those duraloops or some new hi cap d nimh cells work with the terralux tle-6ex, or tle-300 for my 6d mag? Would it draw the cells down too far once the led starts too dim? Or am i better off running alkalines instead? I wouldnt want to ruin any good nimh cells by doing that.
And for my 4d, could i run hi cap cells with a tle-6ex, or tle-300, or should i just use alkalines? i know i could go rop but want to keep it led powered.

Any thoughts or experience with those set ups would be appreciated.

I have no experience with the Teralux dropins, but my 6C has a Malkoff and I love it.

I would put the TLE-300 in the 4d mag with 4 nimh cells for a light cannon that will run for about 1.5 hrs. and use the 6d as a long runtime light with a tl6ex.