I have been using this set up for years without any problems. No clitches ever experienced by me. There is no spark with this system to cause interference during flight. With the set up I have described here you must use 1 battery per glow plug. I have tried it on 2 and you can get them both to glow. I even use 4 2000mah batteries in parallel and it would not make both glow.
This system is very basic. I don't fly for 40 minutes straight. That is how long you get with a fully charged 2000mah battery. I just use it for realiable engine runs. With my 3 engine Savoia the 2 outboard engines pull of of one center tank and the fuel flow is always changing. The rpms may vary 200- 300 RPMs at any one time. So I run these engines rich. The glow on all the time just makes sure the rich mixture does not cut off the engine.
If you see the need to spend the money on a of the shelf item, more power to you. I just don't see paying $40-$60 for something I can do for $12.....

I also use the Hobbico Quik Field Charger MK ll to top offf the batteries after a couple flights and it works great......


Ty