The best of luck to you with that rifle... looks like a winner!
Those reneagdes are nice rifles for sure. I love them.
If that poses a problem with the space, you have some options.
You can try 3F, a little thicker of a powder, or keep using the setup you are using now for this year. The 3F is thicker, will ignite for you and won't fall down that crack as easily, if at all... might be worth a shot. I would try it for sure.
There was a memeber on here, pa cherokee, in the for sale section selling a flintlock barrel. A .54 caliber for your gun. Might be worth a shot.
Or have a gun builder possibly look at it and try getting your lock assembly and pan closer to the barrel.
If it were mine, I'd use that thing for this season, prime right before you go to shoot at a deer. Sounds tough, with movement involved, but I know you can do it... it'll rule out the possibility of the powder falling out. Alot of guys won't prime until they see a deer and are ready to shoot (still hunters and stand hunters)
You can use the 3F in the pan and see if that stays in better... it will ignite with that.
But I would definately look into picking up that barrel off of pa cherokee... that way, you will have the smoothbore and the 1/48" twist barrel. 2 barrels is never a bad thing.
They have them on gunbroker.com on a regular basis for .50 and .54 caliber renegades. I built a left handed one from all parts... all from gunbroker.
Here's the link to the fellow member's thread... I'd contact him and see if he still has the barrel.
But without a doubt, for now, you got yourself a rifle you can definately shoot into the kill zone, one that looks great and one that will do the trick for you.
Those are just my recommendations... you have lots of options with that. I would try the 3F idea first. Big difference between 3F and 4F size, and by the sounds of it, the space you have, it just might be what you can do for the quick fix.
Good luck with it... and hopefully you can lay the rock down on a nice deer!!!