Hi Steve,
 
I did not ask when did Lancair made the change but the Drawing they emailed me has 8/8/06 on it.
I also noted that when I took out the old spring washers some of them were almost flat which tells me either they need to be replaced periodically or better to search for a better spring. for example something similar to the double coil or triple coil springs in engines, These are cycled hundreds if not thousands times an hour for many year and still maintain their ratings!
I think we are looking for a 500 Lbs work rated spring when it deflects about 7/32 inch. I am no engineer or tech but I arrived at this number when I realized when the current spring is compressed 7/32 is equivalent to 3 times the distance of flattening a single  washer (each has a rating of 170 Lbs to flatten it).
Kamal
1104T