The pitch trim problem with the Mossie isn’t because the model in DCS is super accurate to the real thing, the problem is it’s not.
In the real world Mossies trimming is done by turning a trim wheel just like in most aircrafts, the wheel hasn’t got set positions so you can turn it as much or as little as you’d like.
In the sim however most ppl haven’t got a trim wheel to turn, instead you have to push a button. How much the trim wheel moves when you push that button is not in any way related to the real world Mossie and as of now it moves way too much, so you can’t do the real world equivalent of nudging the trim wheel instead you’re bound to move it a set minimum amount.
You can change this by editing the lua file, lowering the default speed at which the wheel turns when you hit the button, this makes a huge difference, so it has nothing to do with the flight model.