What BEC to use for MMP 1S version?

[simplechamp]

If you saw my thread not too long ago I was asking about the lowest operating voltage for the MMM and MMP since I want to run 2S LiFe packs in my TC3. After some consideration I ended up buying the 1S version MMP. Looks like an awesome controller, as usual, from Castle. Anyone use the 1S version yet?

My question is that I also would like to use the Castle BEC, but will that work with 2S LiFe? The low end of the range is 5V input, and I'd have my cutoff on the MMP set between 4.0-4.5V. I know I can't expect 6V from a 4V source (at least not without using one of those 1S boost modules which I'd like to avoid), but I really only need to power the Rx and a small low-end servo. Will the BEC turn off at less than 5V? Or just output a lower voltage? Am I missing something that could cause issues?

Any input is appreciated. Thanks!

EDIT: Also, since the internal BEC is removed from the 1S MMP do I still need to remove the red wire from the ESC to receiver?