I think we can all (well, at least, most of us can) agree that what Volvo did to keep PV trunk-lids open was a fiasco - no further explanation required. I have, however, remedied that situation with gas-spring lift struts on the hinges. All the credit for this idea goes to Michael Krarup in Switzerland, and you can see what I'm talking about at: http://www.volvoclub.ch/Rohdaten/Anschlagbrett/Kofferraumdeckel.htm
My main problem was translating Newtons, which in Europe they rate gas springs in, into Lbs-force, used in the US. With the help of smarter people than myself I found out that the 200N of Michael's struts amount to just about 45 Lbs-force, and that NAPA part #8195669 fits the bill nicely at 18.5" extended and 11.25" compressed. I used their hinge balls as well, rather than venturing out into a wintery junkyard. I made up the anchoring brackets out of 6" lengths of 1.5" angle iron, welding another 1.25" x 3" piece to one of the wings of each, so as to make the struts' attachment points low enough to clear the angle of the hat shelf. The anchoring brackets were attached with three bolts, captured in 6 x 1.5 x 1/8" pieces of flat bar, coming down through the hat shelf. To attach the ball hinges to the lid hinges, I drilled through the lid hinge at a point where an arc with a 2.5" radius crosses the central bulge (ridge) in the hinge when swung from the near edge of the hole that the pin that held the star-shaped detent wheel in place went through. I ground the small end of that pin down a bit to get it and the detent gizmo out. The result was a gratifying improvement. Others have gotten around the trunk lid inconvenience by using a second detent hinge on the passenger side, which is an excellent solution, but the advantage of the gas struts is that they lift the lid quite a bit higher than before, so that access to the trunk is much improved. Unfortunately, the struts don't do much about the gaping upper left-hand corner of the lid. I tried to reduce the gap by shifting the hinges, but no dice. The lid itself is bent after 42 years of having been supported by only one hinge. I suppose it could be bent back into shape, but that would reguire taking the lid off. Next time.
Bob S.