Personally, I leave Combat Trim on. I rarely, if ever, use manual trim.
For BnZ type fighting where you have lots of speed changes, I find combat trim does a good job. The only time I'll kick into manual trim mode is if I'm in a knock-down, drag-out, on the deck, stick in yer guts type fight. In that case I use manual trim. Also, keep in mind that manual trim does NOT take your flaps into account. For this reason, if you are fighting with some flap popped, it is a good idea to use manual trim to keep it in trim. It depends on the plane though... sometimes a notch of flap will give you a nose up condition, and sometimes nose down. In a slow fight, nose up is OK, but nose down is bad. Make sure you know what putting flap down will do to your bird, and be sure to kick the manual trim in to compensate for it.
I actually don't use manual trim as much as I should. Partly that's because a low slow Jug is a dead Jug so I try not to get in that situation in the first place. The other part is that I'm lazy and I just forget. It's gotten me killed a couple times I'm sure, but no big deal.
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Sean "Lephturn" Conrad - Aces High Chief Trainer
A proud member of the mighty Flying Pigs
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