1. For 4 engines, are you using 4 servos ?
2. Are you using program mix for all 4 servos?
3. Do you use throttle Curve for each engine/servo?
4. Are you using glow plug Driver so that at idle, the glow plug will lit ?
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I'm not building the JHH model, but I'll take a stab at a couple questions.

1. I'm using a mini servo for each engine, located behind the firewall. Tight fit, but short hook up on linkage!
2. I'm not using any mixing for the engines. The set up is working good and they are all pulling together enough for my
satisfaction. I was prepared to resort to one of those "Matchboxes" if this didn't work. Didn't want to do that, because it
would have required a separate wire from each nacelle to the center section of the wing to connect to the box.
3. I'm not familiar with question 3
4. I am not using glow drivers on mine. the engines seem to be very reliable as is. Of course, my engines are set at about
80 degrees from vertical. If they were inverted, like some on here are doing to hide more of the engine, I'd probably do
the glow driver thing. I've never had any luck getting an inverted glow engine to idle without a glow driver.

The reason I didn't mount the engines 90 degrees is simply for convenience of getting the glow driver on the 1,2 & 3 engine. Learned my lesson on that one from my Top Flite DC-3. Had to buy a short glow driver to get in on the port engine between the fuse!