I put together a H9 PT-19 with an OS 46 LA.
When I checked the CG it was way too tail heavy. I had to add 3-4 oz to the nose to get close to the spec C/G of 2.5'' from the LE. This is after moving the motor forward.
Is this normal??
Is there a replacement needle assembly that goes into the venturi to replace the stock remote needle asembly?
3-4oz is excessive but it is what it is.
Test fly it that way and then try slowly moving CG aft and/or with elevator control horn/pushrod hole changes as necessary.
On the other it takes finding a spray bar the right length and dia.
For me the Super Tiger are usually best for several reasons and have been made in various lengths.
O.S. and Enya are good and so is the McCoy and others. Sometimes a Fox is great and sometimes not.
( My info base on engine and related is old school and know nothing about new stuff.)
Wish I could be of more help on this.