As coordinated previously with Alan T, I am powering a geared brushed Astro 25 with two 3S 2220 mah lipos in series
(25 volts) using an Astro 211 ESC and using an Optima 6 Lite receiver, powering the servos with a Kool Flite UBEC and the receiver direct from the motor battery through the SPC port. The throttle signal output from the receiver is fed through a Li-Saver (not shown on diagram) from which provides a low voltage cutoff feature that the old ESC is lacking.

When I plugged in the motor battery, nothing worked except the UBEC got very hot and started to smoke faintly. I disconnected the battery and let the UBEC cool off. I found that I had the connector to the SPC port plugged in backwards which somehow caused the UBEC to get hot nearly letting the magic smoke out. I disconnected the battery and let the UBEC cool. When I plugged power lead back into the SPC port with proper polarity, everything worked normally and Kool Flight UBEC stayed cool. Moral: Make sure to get the plus and minus orientation of the SPC pigtail connector correct before applying power.