I also agree that the OS A3 glow plug is too hot for this engine, as it is OS' hottest two-stroke plug, even with as little as 5% nitro. The OS #8 is the right heat range, as is the Enya #3, but the K&B-1L is also the right plug, yet it costs less than half of the aforementioned brands.
You get nothing by paying more, in any respect.

It was not too long ago that you could buy 12 glow plugs for $10...
In the case of the OS #8, or the Enya #3, it wouldn't even be enough for two...