Thanks again for the input. I reached out to Horizon Hobby which is the US OS rep and they identified the following differences:
"The 60FP backplate is not a compatible replacement. The 60FP uses M4x10 backplate screws, the 65LA uses M3x12.
Thank you,
Rick V.
O.S. Engine Technician
Horizon Hobby, LLC"
Steve, you called it.
Cheers, Andy