freeze plug issues

[68black_betty]

a few weeks ago, i blew out a freeze plug goin down the road, i replaced it with one of those neoprene ones that expand when you tighten them jujst yesterday i blew that one out goin down the highway, now with that being said, before the first one blew out about a week ago my thermostat it was a 190, so i replaced it with a 200, it was either 160 or 200, what im thinkin is would it be possible that with the engine running only ten degrees hotter could expand it that much more to blow out a freeze plug, i checked the other ones and they havent budged at all, or are those neoprene ones just a pos, and does anybody have a tip on how to keep them in, a buddy told me to get one of the steel ones and put some locktite around it