I would add a personal preference to my advice about buying a flinter over a capgun. I would ask (beg) before I say this that no one take it that I'm disparaging their guns. I've already had one forum member blocked due to his tendency to bring up or reply to certain topics for the sole purpose of starting WWIII, and I'll quit, myself, before it comes to me going there.
That said, it is solely my personal preference to build rifles with medium-to-large-sized locks on them. I have very little experience with CVA flinters and none with T/C rocklocks, so if the common consensus is that I'm full of it -- so be it. But I did mess with a Dixie Early Lancaster flintlock, a small Siler and a couple of CVAs I put on pistols, and comparing them to the large Siler and larger locks I came up with the following formula: large flint + large frizzen = more sparks = better ignition, all other factors being equal.
Plus the earlier guns tended to have bigger locks, which may or may not be a consideration for you.
I will also note, before someone else does the favor for me, that neither T/C, CVA, nor other makers of flinters with smallish locks would be overly popular if there were serious ignition issues. All of the above, again, is merely my own opinion.