Just to add my bit to the discussion on Shottky diodes, I have made up a test installation but not flown it. This is because the diode (handily produced in a two-in-one case) drops around half a volt. Hence an ESC supplied standard at 5V output gives only 4.5V at the receiver. I reckon a 6V supply would be needed for safety, supplying 5.5V through the diode... and I don't have ESCs that have switchable output.

I have always used two ESC BECs twinned in Y-lead without problems... hence I don't understand what the OP did wrong at the start of the thread! (From what info was given)

It is always wise however to ensure that each BEC is capable of supplying sufficient current for the onboard equipment on it's own since component tollerances may mean that one will turn out to be supplying most of the current anyway. Bear in mind too that running the onboard radio on a higher voltage will cause it to draw commensurately higher current - and plan for it.