It depends on your goal. Just adding watts doesn't add performance. You may get to climb vertically longer with a large diameter prop with lower pitch, but is that true to the airframe? Personally I think that would be more appropriate for the modern flying whales than a classic.

I would go with a higher-pitch prop to get the airspeed up and fly it more like old (real?) Pattern.

The SF props may pull more amps but you get a lot of thrust for it due to the wider chord. Thrust isn't all you need, though, you need pitch speed as well. I need the SF props on my Gulfstream because of the fixed gear. A 7x5SF trimmed to 6.5" seems to be what is best for my setup.

And yes, 320W is way more than the motor is going to like for very long, and more than the airframe is going to need up front.

I have to put a cooling air intake on mine now.

Andy