Thanks fredsedno.

I have seen in this forum others suggest using the GP RV-4 cowl on the H9 RV-8 because supposedly the GP RV-4 has more room. I dont know if that is really true and for me using the GP RV-4 cowl on a H9 RV-8 is not an option.

I appreciate your help and will update the post with my results. I expect the model to arrive next week. so hopefully in the next 3 or 4 weeks I will know something.

Maybe someone will read the post who has tried an OS55 ax in the RV-8.

thanks again