We ran pretty hot plugs for that altitude. For my mini dragster motor bike. I run as hot a plug as I can get. I am also dumping fuel and oil in this pig ''two stroke''
In all our small two stroke engines we ran a spark plug with a protruding electrode. Those plugs stayed clean and fowled less than everything else would in a small two stroke.
Looks like this. This is just some generic picture. Yet you can see what I mean . The insulater is slighty past the threads.