This will have the opposite effect that you described expecially that high a ratio. It will destabilize the landing approach. You are clutching at straws to fly the airplane in an area too small as described by you in another thread.

Key to landing any aircraft full scale or model on a short field is not destabilizing the approach with a chamber mix to the elevator. No what you must do is stabilize the approach.

Now one additional thing you can try is to reflex the ailerons a bit but not mix them to the elevator. Simply extend the aileron pushrods both sides the same number of turns to effect the trailing edges to be up no more than 1/16 inch at the trailing edges when in neutral.

This is a popular rig for our racing and sport flown Pheonix Strega's....

However in the end I must say it agine if your flying spot is truly only a hundred and fifty foot runway and thirty foot trees as you described then no amount of gimmickry on that airplane is going to help in fact mix's are going to make it worse. Of that I have no doubt.

John