I'm wondering how it failed.. obviously it got brittle and tends to crack. One thought was engineering supports or "covers" which would surround the failing pieces, allowing you to use some plastic bonding glue to melt everything back together for greater structure, etc.
So one thought was using my 3D printer to recreate the whole thing, or probably more realistically, using ABS plastic filament to "reinforce" the existing structure. I'll have a better idea after Diableclyde's pics and once I probably pull my flaps out this weekend.
Here are photos I took tonight at your insistence. I just don’t have time before my trip tomorrow to get any more in depth than these photos until I get back. I also want to put some thought into redesigning or using JB weld to fix what I have.
first two pictures are the broken drivers side, notice the metal bar makes a 90° toward the rear. notice the broken piece has not come off the metal bar so I will need to remove it and try to plastic weld it back on my triangular flap. notice in the one picture, on the left side of the photo, you will see a longer metal rod roughly horizontally. That is the connection for the other side of the triangular piece. If you look closely at my photos above of the broken triangular piece in my hand you will see a circular clamp that the rod would go onto. notice it is split in the back purposefully in order to fit on this rod.
And, here are photos of the not-broken passenger side. Note again that the rod that comes up from the interior mechanism is pointed 90° toward the rear of the car. Notice the somewhat flimsy hinge mechanism visible above it. It is hard to get to this piece unless the Spyder top is in its halfway position. I think the structural problem with this triangular leather-wrapped flap lies in someone leaning on this flap or pushing down on it and the only thing holding it up is this single bar coming up from the internal mechanism, but supporting it only from one side of the triangular flap. Recall, the other side of the triangular flap is just clipped on the metal rod visible in my above post. This creates a twisting moment that I believe sheared my piece. Notice the actual design of this piece that fits onto the 90° rear pointing portion of this rod is trapezoidal shaped and somewhat stout looking. (don’t you dare laugh: I’ll bet not a single one of us has used the word trapezoidal in a sentence for 20+ years! ). It did not break in the mechanism, it broke where the trapezoidal piece is connected to the relatively flimsy hinge of the triangular flap. (And yes, I used it twice, 2 instances of a 5-dollar word equals $10. I think I get a prize.)
All that said, this piece is not exposed to the sun unless the top is down. Most of us don’t leave the top down with their car parked out under the sun for long periods of time, self included. The plastic in my flap that I show in my hand is not at all brittle even after my 12 years. It seems close to brand new and to have broken not from engine heat (in this location there is next to none) or UV rays (leather covers this piece so there is none) but from possibly someone leaning on it or some other downward applied force.
for this reason, may I suggest all of us to look for stress cracks and to get in there with some grease and force grease in along the rod as shown both where the clip is and where the broken trapezoidal (3x=$15) piece attaches.
my geometry teacher would be so proud. She was kind of cute, too, but I digress.
I'm leaning towards some sort of reinforcements or possibly cut/fuse with new pieces. I'm going to have to remove my flaps for some measurements, but have a few things on the front burner, hopefully will get to it in the next week.