I've got a range of them from .40 to .90, all ringed.
Once set up they are magnificent and whats more, don't need buckets of nitro to perform.(5% or less is all they need)
I use Enya 3 plugs in all of mine.
And they do not suffer from peeled liner diease.
A new piston ring and a set of bearings and the engine is ready for another 4 years of flying.
My favourite is the G.51. It is a real powerhouse and stands its ground along side anything OS and TT can throw against it in that class.
But there is a downside and that is that the ringed versions need a long time to run in. Much more than an ABC engine of any brand.