Hi Z.
The extension will be on the way tomorrow. Remember, you will not need it for the OS 32F. From what I remember, the 32F and the Fox 35 w/extension fit in pretty much the same place except for NVA location.
As to the Maple Mounts, I will check my plans to night. !/2 X 3/8ths should be more than adequate. I undercut the mounts 1/8th where the tank will go leaving them 3/8ths square there.
Let me check tonight!
Bill <><