In order to salvage the outside pane from my earlier disaster, I decided to use just the single pane with enough butyl to hold the single pane and gasket in the frame, per this drawing (the solar film is not shown, but it's on the inside face of the glass and extends under the butyl):
This turned out to be workable, but not such a good idea. The butyl is not stiff enough to resist the frame pushing it inwards. It took a lot of pounding on it with a wood block to stuff it into the gasket frame. Also, the aluminum tape isn't all that strong. It does provide good protection from the sticky butyl, but slips on the glass and tears if you try to move the butyl too much at one time. I'm not even sure it's stable--hot weather may allow the butyl to creep partially out of the frame. The other bad thing is you are now assembling the unit with the solar film exposed. Easy to ding. And it's under the butyl, so difficult to replace. Looks great, but BAAAAD idea.
The interior edge looks like this:
If I had it to do over, I'd get a gasket that just fits around the edge of the glass, then use a 0.25" foam or rubber rod, pushed down between the glass and inside edge of the frame, to hold the glass in place.
Zep