Hmm.... would you be able to get seasonal plates? Here in Germany you can register your car for just a few months, for example from April to September. The plate has embossed on it the months that the registration is valid, and then you only pay insurance for those months. Many people with convertibles or motorcycles do that here.

A friend of mine has two cars - a nice one for summer and an old beater for winter. They are registered with seasonal plates so that in the end he always has only one car on the road. (and only pays insurance for one car at a time without overlapping.)

I have no clue if Oregon allows such a thing, but it doesn't hurt to ask. The trick lies in registration. If your car is registered for year-round, then it must be insured for the whole year.