Most of the pattern guys in the Texas running the Webra 1.45/1.60, OS 1.40 and Mintor 1.40/170 seem to use either Magnum or CoolPower (10% or 15% depending on the temperature, 15% when it's hotter)

Personally I'd go with the pure synthetic oil rather than the blend to avoid varnishing the engine.

As to the comment about running more oil in the engine, it isn't a good idea to add too much oil, most of these engines shouldn't have higher than 18% oil. The theory is that they actually run cooler on slightly less oil, 16% or 17%. It's probably not a bad idea to break-in with 18%, but I don't know if it's necessary.

Regarding rusting bearings and your climate, you should expect your original bearings to need replacement in no more than 50 flights, maybe as few as 30. With these engines you definitely need to learn to replace bearings because it seems to be a frequent process. I suggest running it dry and using after run oil (especially in your climate), but it won't prevent rusted bearings, maybe just delay it slightly.

Keith