Update... I ended up mortising out the entire rr channel inside the forearm because of the severe angle at which the original channel was drilled.
I waxed the back end of a 3/8" ramrod drill bit, slid it into the mortise and filled it with acra-glass. I capped it with a piece of maple and clamped it in place. I rotated the drill bit 1/4 turn every hour for 3 hours. At the end of the third hour, I saw that if I didn't remove the bit then, I would never get it out. The acra-glas was adhering to the bit!
After the acra-glass cured for 24 hours, I reamed out the hole with the drill bit and, Viola, it worked perfectly!
Thanks to everyone who weighed in on this. Rick