Prop Selection on Shearwater 25LTZ??

I recently purchased a 2013 Shearwater. Yamaha F-300XCA. It came with a Yamaha Saltwater Series 3 blade 19 pitch prop. My first day out, I noticed that it took allot for the boat to break over on plane, and required allot of tab to stay on plane below 30mph. 3500 rpms is roughly 30mph. I was thinking of trying a 21 with a little more cup to get some stern lift, and hopefully not have to use as much tab. Any suggestions or experiences?

Prop Selection on Shearwater 25LTZ??