I know what you mean about decals, I think my days of heavy mods to existing engines is about over because of the difficulties getting the paint/decals/parts to complete a project.
I put some cloth athletic tape inside the boiler in place of the felt, but it didn't cut down the noise. Now I'm thinking a piece of sticky-backed 2mm thick foam, they sell it at Walmart.
I ran the engine without the lead weight and it pulled 3 MTH 18" Premier passenger cars around with ease. I'll have a 5-car train and think I'll leave the weight out for now.
Hey George, did you ever decide which sound file you'll use?