Watch me helpfully return this thread to the original topic:
I did a lot of research when I posted this original question. At the time, Rock Auto did not have a listing for lift supports for the Crossfire convertible trunk. They do now, and I just ordered a pair. There was a point where Rock Auto had a pair listed that looked like it was for the convertible, but they were actually for the coupe. I ordered a pair, and so now I have an unused new pair for a coupe.
Stabilus always had an appropriate support, because they manufacture a whole line in 10-lb. increments in various lengths. But they would not tell end users what that original spec was. And they’d spout inane garbage about liability if they suggested an appropriate force, or released the original spec. I think they were either contractually bound not to give out the original spec, or they were just so worthless they wouldn’t.
At any rate, I just guessed & bought a pair of 20-29 lb. struts (Strong Arm brand, Part #F4057). They are 10” extended, 6.6” compressed, 3.4” stroke. They’re too weak. They hold the trunk lid up, but they won’t push it up. I installed them last fall (2015), but after just one winter, I have to forcibly pull the deck lid up just to get it to come up.
The new ones from Rock Auto come next week. I'm looking forward to seeing how well they work. If I were ordering a replacement from Strong Arm (through Advance Auto, for example), I'd probably step up to 50 lbs. force (F4059).