Well I think Ive reached the end of my Joe's build log.
After 3 versions and several sub versions, I now have a functioning dust shoe that Im happy with. Pic is of the final R & D design just after I had finished cutting out a part (I havent cleaned work area), I will now build a nicer more refined version of it for final use. The little rubber skirt is held on with velcro so you can open up the front and easily see in to set the Z to 0 on the material. I have made 3 versions of the skirt in S, M & L so depending on what length bit I have to use I have a suitable skirt.
So far it has worked very well and nothing appears to escape it's vacuum.
The machine is running a treat, cuts really well and to an accuracy far better than I will ever need.
If I do anything else with or to my Joe's worth mentioning I will post it here. Thanks to all those who have shown interest and provided input and encouragement along the way.
Thanks Joe for a great DIY design.
Gully