The Armstrong on my '77 Excella 500 has 4 screws in the top of the shroud. There are 2 toward the front and 2 toward the rear. There is no framework around the edge to hold the front or bottom edge of the shroud to the trailer.
'01 2500hd ext. cab, 8.1 litre gas, 5 sp. Allison auto
3.73 rear end
Mag-Hytec rear diff cover
Amsoil Dual by-pass oil filtration system
Amsoil synthetics all around
265 watt AM Solar, Inc. system