Tinker - sounds like the perfect wad set-up. The way the wad is forced out onto the barrel is an excellent idea.
: If you want to try a home made lube that I've found to work incredible with ctg. guns and ML's with slugs, it's the 60/40 beeswax, vaseline. I got the formula from Paul Mathews books and it works splendidly. You can vary the beeswax or vaseline up or down, depending on how hard you want it. 60/40 makes for an easy lube to use by hand.
: Another one is 3 ouces Beeswax, 6 ounces Castor Oil and 2 ouces Murphy' oil Soap. Melt the wax and add the Castor oil, then when hot, add the Murphy's and whip the combinaton into a lather, pour into containers and let cool. Again, the amount of wax can be reduced to soften the lube. The above will make a relatively hard lube. The murphy's is necessary as it combines the wax and castor which won't blend without out. It's a good lube, and may make a good water proofer for boots as well.