Yes...

I'll be running the HS-5085MG, I think it should. So, if I have this hooked up and decide to do some bashing at 2S, do I have to remove the ParkBEC? The 6V ones says something about not working with 2S packs.

Yeah, pretty much any switching BEC needs at least 1.5v higher than the output to work right. If it has a 6v output, you'd need at least 7.5v all the time, which won't happen for very long on 2s.

The one nice thing about the DimensionEngineering BEC is that it has a throttle signal pass-through feature. When using 3s, you hook your throttle to one side of the UBEC and the other end goes to the receiver. Use something like a servo connector, mini Deans, etc for the BEC battery wires so you can remove it easily. So, when you want to run 2s, just remove the BEC and plug the throttle cable directly into the reciever.

OK, so I will wire it in with a quick disconnect of some sort. I'll be running this with a Ko Propo 2.4Ghz receiver (KR-407S). Can I mount the BEC right next to the receiver, to make it easy to swap the ESC from the BEC to the receiver quickly? Or will this cause interference?

Thanks again for all the help.

You should be ok. 2.4GHz is quite resistant to noise (at least at the frequency the BEC runs at), and the DimensionEngineering BEC is just about noise-free. But you never know. Try it and see. If you have range problems, or other odd things, let us know because there are things you can do to reduce/eliminate the noise depending on where the interference is coming from...

Alright, sounds good. I want to mount it right next to the receiver, just for packaging reasons. When I run 2S, I can swap the esc plug from the UBEC to the receiver and be all set.

BTW, I found somewhere else where somebody had mentioned the EZRUN LVC does work at 4S, so I should be all set.

Just gotta decide which Neu motor I need now, but that's another post...

Thanks again.

why should that matter? the ubec/external bec is providing 5v current, no matter what throttle the esc has.

Well no, the BEC doesn't matter, but the LVC part does. Aircraft throttle signal goes from 1ms (neutral) to 2ms (WOT), but cars go from 1ms (brake/reverse) to 1.5ms (neutral) to 2ms (WOT). When the LVC kicks in and goes to neutral, it would actually be sending a brake/reverse signal to the ESC if this was used on a car ESC.

aha. I used to have this indiv. lvc-thing (made by "robbe"), but never got it working properly on my cheapo-plane esc. or I am too stupid... it has a button, to do a setup and to "tell" it what to do when there is a lvc.
fortunately, the lvc of the esc works well.