(This picture shows the bottom of the cookie sheet after it is installed.)
Take your cookie sheet and draw a grid of 1" squares, now drill a 1/16" hole at every intersecting line. Drill some pilot holes every 2" along the lip of the cookie sheet to mount it. Later you will be mounting the cookie sheet upside down onto the 1/4" plastic.
On the plastic sheet, cut a hole in the center that the vacuum hose
adapter fits snugly into, but do not mount the adapter yet.
Build a box 12" high, 19" long and 13&1/2" wide with no top or bottom out of the plywood (just the four walls). Glue the hose adapter in the plastic with some Krazy glue. Make sure it is close to flush as you do not want the adapter sticking through the plastic more than 1/8" on the vacuum (top) and seal around it with caulk. With the adapter facing down place the plastic on top of the box, drill some pilot holes and screw it down.
Cut six little blocks; about 1/2"x3/4"x1/2" and glue them about 4" apart on top of the plastic with some caulk. These will be supports to help the cookie sheet maintain its shape under stress.
Place the cookie sheet upside down on the plastic, test fit, then glue it down with a liberal amount of caulking, then screw it down with the round head screws. you now have an air tight metal vacuum table that is only about 1/2" deep and very efficient.
Cut a mouse hole shaped opening [see left side of picture above] on the 13&1/2" side at the bottom of the box for the vacuum hose to pass through. The box is 12" high so that the hose will curve gently and not crimp.
The electric grill will be mounted upside down 2' over the vacuum table. just assemble the the heat shield and heating element on the grill; you will need some extra bolts to do this because you will not be using the legs. Bend the the heating element support inside out and mount it over the element, remember that the unit will be hanging up side down. You won't need any other parts of the grill.
Cut 4, 3' lengths of the angle stock and mount it on the corners of the box going straight up. The grill isn't 19" long so use the 2, 1"x4"x13" pieces of wood on the sides in between the grill and angle stock. Use the wood to mount the grill with bolts.
Make two identical frames from the screen window frame kits, they should fit over the raised part of the cookie sheet and inside the angle stock. This way the plastic will contact the raised edge of the cookie sheet forming a seal.
Remember to cut out a space for the power cord/temp controller in the wood on one side. Now open up the temp controller/ power cord and take out the thermostat, completely bypass it and rewire the cord direct. Close it back up. The temp control will cause it to shut off sometimes and you don't want that.
Mount the socket on the front (19" side) as well as the two light switches. Wire one switch to the grill and the other to the socket. Do a test. Turn on the grill. Then turn on you shop vac switch and plug it into the socket, then turn the socket switch on and viola the shop vac comes on.