I've seen photos of hunters from the southern Appalachians with ramrods sticking out beyond the muzzle. There is a famous one of a barefoot kid with a rifle longer than he is tall. However, I agree with the majority (above) who believe a rod protruding beyond the muzzle will be a pain... It will find things on which to snag. If your rifle is empty (unloaded) and you put the ramrod in the bore, and you have anything at all there to grab and pull it out, the rod is long enough. Your load height will increase the amount of protrusion, as will a jag. Just for loading, you can use a plain old 3/8" ramrod blank, with no finish and no ferrules or anything else on it, if you just want extra length. Cut the dowel to any length you like. It will work fine as a ramrod. We discussed cleaning rods, range rods, and ferrules in a separate thread.
Deepening the ramrod hole in the rifle seems pretty radical to me, especially if you are not properly equipped for it. There are a lot of ways for that project to go south in a hurry.
I would respectfully suggest you get a range rod to bring with you and go try that rifle out, and not change anything until you are certain that's what you need to do. Let us know how it goes.
Best regards,
Notchy Bob