On the club site there is a sidebar that lists good stuff including the glow plug info. Click that. In short, here is what they say about plug types:

RC RULES OF THUMB TO LIVE BY

" Use a hot plug with low nitro (less than 24%), and a cold plug with high nitro (more than 25%).
If you remove the glow starter from you idling engine, and notice an immediate drop in RPM, you may need a hotter plug or more nitro.
If your engine has a tendency to backfire a lot, you may be using a glow plug that's too hot, or you may need fuel with less nitro.
Most hot plugs can take up to 2.0 volts starting power without burning up, while most cold plugs prefer 1.2 to 1.5 volts starting power.info/links. "

So, you should be OK with up to 24% nitro. But use the guidelines to see what heat you should be using. Note that they are 2 volt plugs, I use a lead acid gel cell battery with adjustable current to the plugs through a panel on my flight box, so no problem for me. A 1.2 volt NiCad or NMH glow igniter battery may not heat it up enough.

Another thought: These are long plugs with an idle bar, on some engines (OS) they may be too long and may hit the piston top. Check this carefully before starting or even turning the engine over. If the plugs are too long you might try to use an extra washer or two to "shorten" the plug reach. Others are welcome to comment as I have not tried this myself (yet).

Sincerely, Richard/Club Saito #635