I also recently bought a used Scout fairing, and the only installation drawing I was able to find was this not-very-helpful drawing from a Triumph message board:
http://www.triumphrat.net/images/attach/pdf.gif.
I won't be back home until tomorrow or Thursay. When I get there, I'll be glad to take some pictures for you and more accurately describe how I mounted it. Let me know; I'm (same username) at cruzio dot com.
If I can remember: the four rubber-faced 1/2" washers are used under the nylon sleeves to mount the windshield to the middle piece; a plastic cover snaps over the nylon sleeve to cover the bolt head; on the inside, there's a 1/2" washer (no rubber face) and a nylon nut on the inside.
The middle piece mounts to the fairing body with more bolts through nylon sleeves, washers, and metal nuts.
The fairing body has upper and lower mounts. At each of those mounts to the fairing, use a big rubber washer between the fairing and the angle pieces; the bolts pass through a nylon sleeve, the fairing, the rubber washer, the angle, then a washer and metal nut. The same black plastic caps snap over the nylon sleeve to cover the bolt heads. These bolts don't use the small rubber-faced washers.
The upper mounts connect via curved flat stock; the curves are mounted convex, that is, they bow outward towards the side of the bike.
The lower mounts are aluminum angles; use a big rubber washer between the angle and the fairing body, adjusting the pieces for the best (flattest) possible mating - I ended up bending the angles a bit.
The headlight must be unbolted, and flat stock aluminum extenders now bolted to its mounts; the headlight is moved forward a few inches and bolted to the forward lower hole on the flat stock; the rear of the flat stock has two holes for bolts (if my memory is right) that screw into the headlight ears. (I'm getting fuzzy here...)
I changed a few of the bolts to rationalize their heads, so that I could remove them all with fewer tools...like the ones I carry on board.
All in all, it's not rocket science, just oddly tedious. Remember you're dealing with plastic bits, and don't overtighten things - the PO did so on one of the bolts holding the middle piece and slightly cracked the fiberglass gelcoat.
My riding partner also has a Parabellum on his '07, and we both noticed that at full compression, the lower edge of the fairing interfered with the reflectors that are glued to the side of the fork tubes - we could hear a "click" at full compression, and feel a little something in the grips when it occurred. The physical interference was minor, but I didn't like the sound or the feel, and didn't want to remove bits of the fairing. So I sawed the reflectors off with dental floss; they're stuck on with a foam layer that's easily cut.
