Hi Jeffbo,
The problem you notice with the mark silencers (Mufflers!) is far from uncommon, many Mark owners have been seen rummaging in the hedge looking for absent silencers
I have to confess that many years ago I once saw in my mirror our Secretary of the time ducking to avoid my cartwheeling silencer passing over his shoulder! Ah those were the days!!
Seriously, it can be very dangerous should it come off.
The design of the suspension and toolboxes does make an elegant solution rather tricky, various attempts using straps have been tried, either with a strap round the tail pipe or by brazing a lug onto the silencer body as on the Dragonfly, I have used Dragonfly silencers in the past turned so the lug is vertical and attached a strap up to the passenger footrest bolt. All rather clumsy looking.
A thought that I do have is to mount two very small lugs (literally a small "U" shaped piece of thick wire) one on the exhaust pipe the other onto the entry pipe of the silencer and use one of the exhaust springs used on modern bike pipes. These could be tucked under the pipe close to the frame and would therefore be unobtrusive. To avoid damaging the pipes the spring attachment could be added to the exhaust clamp and silencer clamp, not so effective or elegant but less damaging to the chrome!
Have fun.
Dave
