Here's the next round of modifications......
In an effort to get greater load at the very end of the roof travel (when the roof is down) I added some die springs for the last 1/2" of gas spring travel in the track.....this equates to around the last 4" or so of vertical roof travel.
These springs are very high spring rate and are used for opening dies/molds on large injection molding machines. The springs I'm using are 2.5" long and fit in a 1.25" bore and have a spring rate of 1176 lbs/in (wicked stiff!!!!). Usable spring travel is 40% or .5 inches..with a max load of 740 lbs at that displacement.
You can see the spring hanging out of the end of the assembly here.
These come in many sizes, lengths and load ratings and they are color coded Blue, Red, Gold or Green as you increase spring rate and load rating.
I drilled a hole in the end of the track channel and installed a sleeved socket head screw to pilot and retain the spring. At these loads you don't want the gas springs popping out of the channel when compressed. The opposite end of the assembly is fitted with a machined delrin "nose" that fits in the bottom of the crossbars.
Keeping in mind that the entire gas spring contraption will see the max load when the roof is closed (like 500-700 lbs)...it wasn't surprising that I had one fail where the 80 lb gas spring screws into the delrin block when the roof was almost down.....the assembly bowed a bit (I wasn't using the retainer plates above the channel) and the 6mm threads on the end of the cylinder ripped out of the delrin.
I subsequently replaced the delrin blocks with aluminum blocks to avoid this in the future. I also sized the aluminum blocks to fit in the channel and to be retained by the retainer plates.
I'm estimating that I'm loading the die springs to probably 500-550 lbs of so when the roof is down, as I'm not quite using the entire usable 1/2" travel of the spring.
This worked a bit better than the last setup but still needs significantly more force at the beginning of travel when lifting the roof from full down position.