The pull-pull cables should have slack removed but don't need to be "tight", in other words you don't need to have a lot of tension on them. If you're willing I would stick with the four stroke for now. I really like them and still fly two strokes but the sound and torque of the 4 strokes are nice. If you continue to have problems, stick a two stroke in it. Like I said it's about fun not aggravation. You can keep the 72, work with it some and put it in something else later.