I agree, the design is poor

- mine leaked at the top

(opposite the bolt) too.

I removed the mount from the pipe, bent it so the angle on the inside was just slightly more than 90deg and then refitted.

This ensured that the gap at the top was sealed.

It hasn't leaked in 3 years and I have no worries about any extra sealant/silicoln coming off and making its way through my engine.

To echo above comments, use the orange ring too