RE: Adding fuel line filters ...
well I will go against the flow on this one.
I use an inline fuel filter on all my planes. I have never had any problem with a filter coming loose, leaking air, etc. I do clean them on occasion and often find junk in them even though I have a filter on my fuel can.
I havent seen any drawbacks to using them and they seem like cheap insurance to me.
I dont see much use in putting them between the engine and muffler. That pressure is going out and not into the engine. When the engine is not running I think it would be pretty hard for dirt to make it through the muffler, down through the tubing and into the engine. If you are worried about that I think it would be more pratical just to cover the end of the muffler when the engine is stored.