Tom, you might try Amazon or RockAuto and stockpile a few of your desired filters.
Any filter that has matching threads and a proper seal fit will work fine. Any additional oil capacity involved is really not going to contribute much one way or the other to oil cooling and engine life.
A much better modification would be to install an aftermarket transmission fluid cooler for an automatic equipped car and bypass any engine cooling system fluid coolers.
Your transmission would thank you for it and when and if you ever decided to trade the car off you can remove the add-on cooler, reconnect the cooler lines as they were, and keep the cooler for your next vehicle.
How often do you suppose this happens even at independently owned shops? They’re out of the exact part, throw on something that fits, Bob’s your uncle and no one’s the wiser.
I talked to the guys at the local foreign parts specialty store. They had just what the doctor ordered - A Union Sangyo C-840. It’s larger than any of the current filters offered for the 4-cylinder Subaru and looks a lot more like what originally came on the vehicle. It’s also an extremely well made oil filter - I bought two so I could cut one apart just to see inside it. Frankly, this filter is a cut above anything I’ve seen produced here in the US. I was very pleased with the quality and construction. I went back and bought a dozen which will cover me for about the next 50,000 miles.
Also just as a side note - my engine is running just a notch cooler now. For whatever reason. My gauge doesn’t register in temperature, just a hot/cold scale. It was running one notch above the middle line, now it’s a notch below that line and we’ve been recording 95+ degrees all week. Thanks for the ideas, I’m all set now.
If there’s ample room, and the design of the filter is the same, I don’t see any harm. You would get the benefit of more filter material, and slightly increased oil capacity, adding to the oil’s longevity.
The only possible problem I can see is if the pressure relief valve is calibrated to a different value on the ‘wrong’ filter, or if the anti-drainback valve is different or not present on the larger filter.