ORIGINAL: bigtim

my deflector never fell off, you have to crank the zip ties down tightly,I also made sure the tip of the muffler was cleaned with alcohol before I put it on, as well as making sure the size is right for the 46.

like what has been said the Nextar trim covering is pretty poor,but to help the covering and trim stay on, I always iron the covering before assembly of all my ARF planes, to make sure the covering has a good tight seal, just a little bit of a loose seam, the fuel oil gets in there and loosens up the glue,it will never seal down after that.
spray poly will generally stick to plastic film covering and seal the edges,but adds weight.

eventually I ended up stripping the covering repairing some broken areas and converting it to a float plane,for redoing the windows the peel and stick black covering works well you just need to make sure the surface your sticking it too is super clean any grease or exess fuel and the stuff comes off.

depending on the condition of your plane you might be able to repair it so you have some spares in reserve instead of throwing away the extra parts you might be surprised how easy it is my Nextar was crashed and rebuilt several times before I went for the full strip and overhaul as well as adding a OS61 for more power.