Cris,
I didn't look at your post until after you had found what you needed to know. As for the sarcasm, sure, we all participate ans some more that others. I'm a master at it
As for the mufflers, the only impact using two of the same side will provide is in cosmetics. If you don't mind an offset on the bottom of the plane, the plane or the engine won't know the difference. If I was setting up and otherwise had all I needed and wasn't inclined to spend more $$ I'd just use them. Done that before.
The mufflers provided with our engine are not performance enhancers for the most part. Some custom after market stuff can add or subtract a little. Usually subtract but not add. All they do is relocate the exit location of the exhaust gasses and slightly change the tone of the exhaust process. Where actual sound level is concerned the propeller's blade/tip shape and tip speed will have a much greater impact on sound reduction than a muffler will.
3w makes good stuff so I'm pretty sure you'll like the performance with a matched set of mufflers or two of a kind
