Carby Heat Exhaust Shroud

The above photo is of a G clamp squeezing the top of the carby heat shroud to get some clamping pressure on the exhaust. The lower back side of this shroud has a piece missing so will be coming off again soon. I found the top inner clamps really loose and signs of where the whole assembly has been flopping around so much so that it's almost worn a hole in a relatively new exhaust.

I've looked at the IPC, but that doesn't help. How do I get firm clamping pressure so as the whole shroud is not flopping about. The bottom clamp is firm. I guess that's why the piece has chipped out. Bottom attach firm but the whole shroud moving.

Thanks,
Texmex.