Congratulations, Dave.
I've been running straight 30 weight for some years now with no problems. There has been discussions about some oils used and I can't remember just how it went, but it was either a synthetic or one of the Red Line oil, (please excuse me if I do't have the products quite right) but it went something like the lighter oils or more slippery oils caused the synchronisiers to not work as well because they were to slippery. A local friend, having just restored a MGB used some such oil, and after were talking about it because I had read it somewhere, he said, he was experiencing similar characteristics. He changed out the oil to straight 30# and the shifting got smoother. But i can't remember what he had in there.