Notty

Very rookie question, but for my 8" reflector, would I position the heating tape outside the tube, parallel to where the secondary mirror is, or slightly below or above it? Would this be effective enough to prevent dew on it, or do I need to be looking at a home made resistor type affair of the like I have seen which heats the mirror plate directly (which I'd rather not having read about people nearly setting fire to their scopes!) Many thanks