Humble,
One of the secrets is how much fuel it is carrying at the time. The Mossie carries a max of 540 gallons internally, that is well over 3,000lbs of fuel. If it doesn't need to fly for 90 minutes (and who in the MA needs to do that?) the pilot should always take 50%, or 25% and DTs.
On 25% fuel I fought Eskimo's Bf109F-4 for over a minute I think (it is hard to calculate time in a fight, I am frankly poor at it.), with a lot of manuevering. He lit me on fire in the end, but it wasn't an autokill for his 109F-4 in a close dogfight.
As I said earlier, the Mossie is capable fighter, but far from the best. I think that many people play "goon" in it though. They get attacked and just give up, thinking the situation is hopeless. You can see a bit of this on the forums now and then when people make lists of fighters and bombers in the game and put the Mossie in the bomber category and the Bf110G-2 in the fighter category. The Mossie is, at minimum, as good a fighter (I think it is a better fighter) as the Bf110G-2. But people seem locked into "Mossie is an unarmed bomber that is helpless if attacked and can't run" mode.
Basically there are to modes I fight in when in a Mossie. I either play it safe and conserver my energy if I have a advantage in position and am fighting an aircraft that doesn't dominate it. If I am at a disadvantage I go ultra-agressive, using anything and everything I can think of to kill a fighter that has me at a disadvantage or is a fighter that does everything better as a fighter. The two hardest fighters for me to beat are the La-7 and Typhoon. The Bf109F-4 through Bf109G-10 and Fw190s are hard as well. N1K2's and Spitfires are comparitively easy as are P-51s, though P-51s should be in the same category as the La-7 and Typhoon.