Here are three photos of how I located my ELT Antenna under the canopy of my RV8.

I fabricated a small bracket that mounts between the members of the mid cabin cross bar.

The bracket is angled slightly as can be seen in this photo. While it does momentarily touch the front bow of the canopy as it's closed it does not contact the inside of the canopy at any point so there is no danger of scratching the surface.

The rear passenger when entering the aircraft does need to be careful not get hung up on it but that's the only drawback I see.