Once again, thanks to all for your thoughtful replies.
I have advised my friend to take a long hard look at the GPR. He's kinda set on the "Hunter" version, so I've got to get him out shooting PRB so he can see that it's fun, accurate and cheap. Hopefully that'll change his mind and get him to go for the slow-twist barrel. The next thing we'll have to work on is a better sight set, or at least some paint on the sights because the factory sights look to be hopeless in the bush. I could hardly find them when sighting the rifle in the store. Hmmm, a couple of coats of white paint, followed by a couple of coats of flourescent paint should help that little problem.
Daryl - you mentioned your brother sells english flints. Around here about the only flint one finds is in a blister pack at the gun shop. This looks to me to be a losing deal as I'd want to have a handful of spare flints, just in case. (Don't ask "in case of what". Just in case... LoL) If your brother is in the business I'd appreciate any contact info you might be able to provide so we po folks in the east can get hooked up with a good source of supply. Also, our trip to London got messed up so the time in between our pistol matches didn't happen. Bummer... I really wanted to get some more BP cheap. But one of my fellow pistol shooters called me today and said he had a bunch of powder he wanted to get rid of. Looks like I might get it very cheap.
There was a comment made about trigger adjustment - if it's as easy as the screw substitution suggested then it's a pretty minor concern. I don't mind fiddling with guns to make them work, but I don't have a machine shop handy to completely replace a poor design. I guess that's why my competition pistols have electronic triggers...
And thanks too for the clarification on the slot in the touchhole liner. I've already received clearly the notion that the touchhole should be opened up a bit for more reliable ignition, so I'd pretty soon find out how to remove it.
Once again, thanks to all for your kind words and experienced guidance.