Probably a good idea, and agree that now's the time, Bill.
I can't think of any of the engines that are in use that have provisions to attach a muffler. If they did, it would be a very nice feature and I'd sure be willing to try it. But they don't.... (Nelson, Parra, Profi....)
We could probably come up with a reliable way of attaching something useful to the plane on a profile but it would take some work, and would be different for every engine so guys would pretty much be on their own, since there just aren't very many out there....
Dave