Here is my US .40 with an Enya .80 on it. I just pulled off the 7 ounce pitts muffler (jeez!) and am waiting on a 3 ounce muffler. With the 7 ounce muffler she needed 6 ounces on the tail and weighed in at 7 lbs which seems excessive because the manual say it should weigh around 6 lbs. I did reinforce it a lot but not that much! I just bought an 1100 mah rx battery and am installing that in the tail today. I might put a servo back there as well if it still doesn't come out right.