The engine should be able to run that prop and a little more. I highly recommend a telemetry module to send you in flight RPM readings so you can tune the engine better. In flight the prop will unload and engine RPM will rise. If you exceed 7000RPM for a while you risk seizing the engine. I had this happen early on because the engine has more power than the factory recommended prop can absorb, so blew the engine. Then I added telemetry and went up to a big prop.
I have a modified FG84 and in flight with a 24x14 Xoar prop it turns 7400 with ease. Im going to reprop it to a 3B 23x12 or an adjustable pitch Solo 3B 24 inch prop and tune it by in flight RPM data.
Oil Im using Klotz Technoplate, so far the best oil Ive run in all my engines. Ive tried all kinds and returned to this. Cleanest running and my engines run hard and powerful. Just take the time to run them in and don't over heat them when breaking in.
The FG90 will not fit in the TF cowl, you probably noticed by now. I had to modify a H9 cowl and the firewall. Mine has zero x zero thrust compensation, flies great, no bad habits.
Awesome plane, crowd pleaser, your going to have fun