You are looking at close to a year of shoots to get good with an ‘87.
Figure the cost of sending it to Lassiter if you want to be at all competitive with it. The difference between the gun from Coyote Cap and Lassiter's work was night and day. He will improve the new guns just as much.
You will be faster with a double, but you will have a lot more fun with an ‘87, especially with black powder.