Yes, a APC prop. I have not tried a 16X8 but I'll bet it would do better than 8900. My engine was put into service this past spring and has had 5-6 gal run through it since. It has picked up about 200 rpm since new. The 17X8 has worked very well on my ultrastick, so I have not tried anything else.
I have a 3W-24 that I have not yet run but I expect it will be slightly stronger than the zenoah. It's not an inexpensine engine though by any means.