As I stated, use them or don't, it's a pilots choice and if it gives a pilot piece of mind then by all means use one. IfI had any multi cylinder glow enginesI would sure use one.
I'm not one of those weight watchers so the little bit of added weight doesn't figure into it for me. The extra weight can be used to help get the CG set. Ihave made up a couple for planes Ihave built for other people and they work out pretty well. Iuse a micro switch and a micro servo slaved into the throttle so at anything under 1/4 throttle the driver comes on.
Ithink if Ibuilt myself a nice scale warbird that I put a lot of time and effort into I would install one. My choice not to use them is not etched in stone. Ihave just never felt the need for one, YET!!