I once watched a model go out of control - (it was obviously throwing all urfaces in wild flail mode.
The post mortom showed that the Bosch metal cap -which was clamped tightly at its base, had fatigued around the slit above the clamp then the cap vibrated around the plug- you could see the scuffing.
The single cyl engine really was a vibrator and tho the owner used a dual RX setup -and had everything else done correctly - the hash generated by the engine running -with intermittant grounding, was too much.
As long a every thing is well grounded ad shielded - you can get away with some pretty spooky component placements.
On my own models - I have had the cap come loose a few times - I use the ZDZCap setups - and they simply flip off the plug and the engine kills.
Never even a momentary glitch.
Even tho the fully captured setup they use , may not appeal to everyone - it sure seems to be the best "trade off " of all the types I have seen.