Hi John, Both the front air gaps and the rear fender skirts were attached by cutting 1" by 1" 90 degree angle aluminum into 1 1/2" lengths and using #6 X 1/2" stainless screws to attach it to the lip of the fenders.
Then I attached a 6-32 stainless bolt with a 6-32 nylock nut to the angled aluminum. the angle was recessed back into the fender lip enough to move the nut back so when the air gap or rear fender skirt was installed with another nylock nut on the outside it would be flush with the fender.
The back boat tail was made of the following materials.
The Kammback part is made from 24 gauge (0.0250 inch) aluminum sheet. The top of the Kammback was a commercially produced "drag racer wing" that was scrapped by someone else in the shop and I don't know were it came from. Here is a picture of one on Xntra's VX with out my added side "wings".
Here is the best picture I have of where I added the side "wings" to get the boattail extended down to just above the taillights.
The bottom of the boat tail (diffuser) is made from 10 mm coraplas, the same as the belly pan so the transition between the two would be smooth.
All the other parts of the boat tail and fender skirts other than the lexan tail light section was made from the 24 gauge aluminum sheet. All this sheet was either scrap or damaged material, so I don't know how much this stuff costs (I was afraid to ask!)
Here are some more detail pictures that may give you some ideas on how to attach some of the items together.
