A couple of things. Byron systems need air. unless the inlets are huge, you need the cheater hole. The rear ducting must be complete. If you are not getting speed on the ground, either the grass is too thick (use larger wheels) or your gear is set up wrong (make sure your main wheels are rubbing on the strut and you have a degree or two of toe in. The rudder is a good idea but not necessary.

I agree the first flights should be on a jet friendly field. Remember once this plane breaks ground to keep your climb shallow and don't make your first turn until you have built up some speed.

Mark