The door windows (0.093" acrylic) were initially match drilled to the outside retaining aluminum with a #30 drill. Then all holes on the acrylic were enlarged to 11/64" to leave clearance with the set rivet body. Image 1 shows the window in place against the foam-core butyl tape.
Image 2 shows the window installed with rivets and engine baffle washers (from aircraft spruce) as retainers. The acryllic is free to expand and contract by floating between the taped aluminum surface and the retainer washer.
