On each side of the canopy frame I put two standard thickness washers between the canopy frame bushing and the fuselage, this didn't reduce the contact between the strut and the bottom of the canopy frame arm. So, I removed them.
Next I put a standard thickness washer between the C-1204 bushing and the canopy frame arm on each side. This reduced the interference. But, didn't resolve it and means that that AN509 screw will need to longer (i.e. stick out more).
I'm starting to think that the interference / rubbing is going to happen and that the best solution is to round the bottom edge of the canopy frame arm so that the strut has smooth surface to ride up on. Or there is something wrong with the parts that I have.