912 UL in trike rpm setting

reduce the pitch to obtain 5200+ on climb

see Service Letter below

https://legacy.rotaxowner.com/si_tb_info/serviceletter/sl-912-016-r1.pdf

and try to get about 5500 WOT level flight

Why do I see a lot of WOT rpm less than level flight? My max rpm is the 5100 even when climbing, and then significantly lower when level. On a fixed pitch prop that doesn't make sense or I am confused. I know the prop tips are set at 11 degrees so I'll look at adjusting that down to increase max rpm.

If your RPMs are less in level flight than in the climb, that is probably because you pulled back the throttle.
When you level out by lowering the nose, the airspeed increases and unloads the prop, allowing it to speed up.

You have a 912UL (80hp), it only makes 80hp at WOT and 5800 rpm.
Unless you can at least approach 5800 rpm at some point during the flight, you are not utilizing the full capabilities of the engine.
Many recommend pitching the prop for 5500-5700 rpm in level flight at WOT as if you are in a race where getting there is the priority.

I recommend pitching the prop for 5700+ at your Vy ( Max Climb Rate) with the understanding that you will need to reduce the throttle as you level out.

This will not maximize your top speed but it will maximize your climb rate.
I like to consider that clearing the trees is far more important than getting there 5 minutes earlier