hi yer sorry would help

most of the time i use to do this test on grass but now i have a table that i use and scale conected to my fence

motor is a mark one or two not sure Irvine 61 normal muffler and i tested 12 x6 11x7 and 11 x 4
with a smaller muffler from a 40 size i was only getting 9000 rev on a 12 x 6 and it would not take off
put on a 60 muffler had to shorten a little to fit and now on a 11 x 7 12600 rev and 2 kg pull on the scales i have not had a chance to fly it yet