~S~
The elevator control in CFS2 (and indeed in CFS1) is a very twitchy and doesn't seem to bear much resemblance to the way it works in real aircraft - not in the few I've flown anyway.
The excessive sensitivity could be due to the repeat that you have set on the trim controls. With full repeat on, holding down your nose up elevator trim control will loop your aircraft! Best to remove the repeat and try tentative little tippy-taps...

Adjusting throttle and propellor pitch helps too - I find if very difficult to trim out an aircraft going at full pelt, much easier at cruise settings.
I also use a simple autopilot to establish proper balanced straight and level flight at times. Once the AP has trimmed you out you can turn it off and the aircraft should remain in trim until stick input takes it out again.
~S~
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