ORIGINAL: unit53
theres another way to keep those muffler bolts tight,,,and that is to make sure your prop is well balanced,, and to cut off excess exhaust tube legnth to reduce the vibrational mass ,,plus this prevents the usual seam failure on the tube anyway,,,your last resort also ,,,you could use longer bolts with some quality washers and lockwashers ,,,not the cheap ones that smash down ,and do nothing.
On mine, I cut a thin aluminum 90' gussett, and heliarced it at the tube joint at the muffler... The gear broke off on a bad landing, and the muffler tube bent back about 45', crushing the canister end......still no leak and it's still flying... this will work....