I have the horner tips on my TF Cessna and they aren't any problem. I guess if you are prone to banging the wings around (hanger rash) you might break them but they are used on the scale plane. I really don't know how much difference they make (can't take them off ).

I had an OS 91 4-stroke on mine at first but it was not quite enough power. It flew very scale like but did not have any resurve power during take off from a grass field. I put on a 1.20 and it is now just fine. However, I did have to cut a hole in the cowl for the valve cover.