In general, an un-cupped prop of a given pitch will act close to a cupped prop of 2" less pitch- RPM wise.
An un-cupped prop tends to be used on stern-heavy boats and is likely an older design. As expected, the nose tends to drop at higher throttle settings as well. Been a long time since I've seen an un-cupped SS Prop.
Wow that's quite a response from the seller.
It might be that simple but good luck finding a prop that is exactly the same on the other characteristics but 1/2" less diameter.
While it might be true dropping diameter will raise RPM's it also lowers the prop's drag and load on the motor. Also lowers the props thrust and acceleration.
I no longer own anything but stainless props. Keep looking. If the price is right try same diameter/pitch/rake/blade type in Stainless. That might be all you need.
This prop business is quite an art form.. Thanks for your experience !