I finished my vacuum box for creating my own airbrushing stencils this morning. The unit is enjoying the sun and breeze while the silicone sealant is curing. I used a pvc floor drain insert the fit inside a wood frame from underneath and and both press against a piece of semi-rigid perforated stainless steel screen. Another plywood cover encloses the drain at the bottom and is fully sealed with the silicone. The pipe nipple at the bottom of the drain fixture accepts the rigid vacuum tube perfectly. When the silicone has finished curing I plan to make a simple plywood tang to screw to the bottom of this so I can clamp the box to the top of the work bench. This will at least get me to the point to see if I need to seal off some of the surface area of the steel screen to help with keeping the vacuum centralized. Its a work in progress but its moving along at a nice clip. I hope to try it tomorrow after fishing in the rain a while. Pics will come as soon as I am happy with the rig.