Lots of good input and for me, I still go back to the individual rifle and what works best. I've never been a fan of tight patching that required a gorilla to get it to the breech - I pretty much have always used what rfd talks about - sometimes going to a smaller ball and thicker patch as I want to load with a ramrod or range rod and not have to "bang" it down. In the end, it's going to depend on what your rifle likes best if you do your job . . . and I'm not being smart when I say that. No load is going to be accurate if you can't hold steady . . . or in the case of many flint shooters . . . if you don't overcome the tendency to "flinch".
Years ago, when I was going to Friendship on a regular basis, I used to watch a guy n the offhand line. He had a custom built half stock percussion rifle -it was a nice looking rifle too. Anyway, I would watch him load and it always made me shake my head. He was using such a tight combination that he had to hammer the short starter with a wood mallet to get it in the bore .. . and then he switched to a brass rod and whacked it with the mallet all the way to the breech. After a couple of years of watching him, I got in to a conversation with him and asked about his tight loads. He told me that a tight load ws the ONLY WAY to load a muzzleloader. I listened patiently and then asked how his scores were . . . he showed me a 25 yard target he had just shot and I'm sorry, it wasn't that good. I said nothing but thanked him of the information he'd given me. IIRC, it was a .40 or a .45 cal rifle. What I couldn't understand was how he could whack on a soft lead round ball all the way down the barrel and then expect it to be round?
I had a smoothbore that I started out using a ball .010 smaller than the bore with a greased pillow ticking patch. Now granted, it was a smoothbore so figure that in. I was not having much luck at all at 25 yards - all over the place. I switched to a smaller ball with the same patch, it loaded easily down the bore (I spit patch between shots) and I couldn't believe the difference in how it shot. My hits tightened up and the only thing I had changed was to go to a ball that was .005 smaller - same patch - same powder load.
The only way you're going to know is to try different patch thicknesses and different ball sizes - and be consistent with the loads each time. There are so many factors that enter in to it . . . humidity and effect on fouling, wiping or not wiping between shots, consistency in getting the ball/patch seated and of course, the individual rifle. I have a flint LGPR in 50 that I bought off or rfd - a nice shooter for me. I can have a LGPR, you can have the identical rifle and another friend can have the same rifle - but just because they are the same rifle does not mean they will shoot the same. One may have a barrel run at the beginning of the production run, one have a barrel from the middle of the production run and the third from the end of the production run. Tool wear can make a big difference in the end product and how it shoots. No different than tool wear on cutting the throats of a revolver cylinder - Ruger is a good example of that as if IIRC, they ream with three different reamers at one time - I have a New Vaquero that proves it.
Good luck with your project and it will be interesting to hear of what you come up with.