I don't think the genuine muffler with Victa stamped on it would any better. The one I replaced on the engine above ^ had the Victa lettering and the neck that goes on the engine had a hairline crack all the way around. The muffler I put on was the older type without lettering I have never seen that cracking on them.
I think what matters is how much packing is in.
I have another PT mower I pulled out after a long time in storage and struck at how quiet it was compared to the one above. That makes me wonder if packing is the only factor for effectiveness.
NormK, can you into some more detail on the gutter beading idea?

Ahh, if only victa had kept producing the thumblatch catcher series, they would be in better shape today!