Occasional starting difficulty with Digital HP CD box in my D200

I have a 1972 D200 that I installed a Pertronix Digital HP ignition system on along with Summit billet (mag pickup) distributor. I have an issue where the voltage to the wire that tells the box to turn "on" sometimes drops below the minimum voltage during cranking. Oftentimes if I crank the engine, release the key (to RUN), then crank again the ignition won't fire and I have to turn the key to OFF, wait a second or two then try again and it'll fire up.

The truck originally had points ignition; I removed the ballast resistor and used a 3-way male spade connector to link the terminals from the 2 sides of the ballast together (start and run) together along with the "on" wire for the ignition box so that it gets an "on" signal whether the key is in START or RUN position. I find that when cranking, the voltage there sometimes drops just below 9V which is the minimum the ignition box needs to see at the "on" wire.

The rest of the ignition box wiring is per the instructions; main power leads directly to battery terminals and trigger wire leads to mag pickup in distributor, plus tach signal. Once running it has no issues (stalling out etc.) and if I go to restart the truck when it's still warm I usually don't have this issue. I searched and saw in another thread that the factory electronic ignition has a 0.5-ohm resistor going to the ignition module so that it sees enough voltage during cranking, might that be my solution? If so where would I put the resistor?