Thank you for your thoughts Deray.
I’m not worried about hurting the board by soldering a wire or two into the power management section.
I am cognizant of hurting the board by applying 5V in the wrong place! 
The “white socket” power connector feeds into a 1117-5 low dropout regulator, whose datasheets specifies 6.5V<=Vin<= 12V, so applying 5V there will not work.
Maybe on the OUT terminal of the 1117-5 might be a good place to feed in 5V.
I’m just not clear on the functioning of the “gate” signal from the LM358 to the MOSFET.
John