OP here. Time to seriously THANK everyone for your thoughts/experience. It has helped me a great deal, THANK YOU! I was on the verge of major regret for getting into black powder/cap and ball because I could not and still can't find percussion caps and powder online. However, thankfully, after traveling on my motorcycle way the heck up, 50 miles away, into the local mountains, I found a retired guy with a gun shop he has open 3 days a week for a few hours in the afternoon and then I scored 300 each CCI #10's and 11's and Pyrodex powder in pellet form. I paid very fair prices(6 bucks per 100 count tin), now I see he was apparently so out of touch and remote that he did not know how retailers are now ripping us off for about 10 times what the prices use to be, disgusting! Next time I go to his shop I will tip him double or triple the cost he charges me. Gold nuggets for fool's gold prices, sheesh, poor guy deserves a break.
Well, little did I know that there is no consistency between manufacturers on percussion cap sizing and fitment. Good grief! But thanks to you guys I am starting to understand the numerous variables involved in this hobby/sport/religion. I am beginning to understand the interest and fun and history, etc. in this endeavor. I never imagined how much fun it would be to wade through a swamp in order to figure out how make these guns go BANG. Very satisfying. I know, I'm not telling you anything you do not already know.
So, after Dremeling my Uberti nips/cones I can fit my #10 and #11 CCI caps and they go KA-BOOM on the first strike with a little pinch on their skirts. I removed my SlixShot nips and will hold them and the Treso nips that I ordered in reserve until I shoot lots more and have a better appreciation for the variables involved with the different nipples/cones, etc. So, THANKS again, Amigos'. I will be back with more questions, that's for sure.