Using wonder-wads over the seated balls causes nothing but problems...SO DON'T DO IT!! Zonie is right, sometimes the wads jump out of the cylinder during recoil. Then they get themselves jammed-up in the forcing cone as the wheelgun cylinder turns to go back into battery! I know this first-hand because I had to take apart my Walker after I loaned it to a friend of mine who didn't understand the proper use of the wonder-wads! This friend wanted to shoot and I thought that they already knew how to use a revolver as they are longer in the league than I, but alas, I was wrong! Nothing really bad happened, just a chore that didn't need to take place during a match, that's all.
Remember the golden rule: Powder, Patch, Ball! Just like with the long guns!!
Keep your powder dry and your wads lubed!
Dave