the bec on either side can fry, or there may be glitching. i've read about it in another forum that has a ton of posts on the subject of 4n1 hacking. most of the latest posts agree that cutting the brushless bec wire yeilds the best results.

theoretically, the bec's have identical output voltages and perfect current balance, so connecting them in parallel would be fine. in reality, no 2 regulators will produce identical voltages at all loads, so connecting 2 power supplies in parallel is hazardous. the imperfect outputs may oscillate, creating spikes in voltage and current which can make the rx glitch or fry a bec's voltage regulator.