I am out of O/Bs at a deal right now I really only acumulated what I had through buying complete units and trading and such If I stumble on to more I will let you know.
The amber seems to be a reasonably good spring that acts fairly fluid off road trail but I kind of stay with what seems to make customers happy with my set ups and that pretty much means 4 ranges here for us. Degree of angle and amount off of spider, bike weight, horsepower, cams ,carbs, porting, Swinger arm or not,Tire of coarse, it all just kind of dictates what I recommend as a baseline setup that most seem to stay with or not venture too far from anyway.
How ever cut and dryed the grams of the weight and roller position on it is the main player and static spring tension just kind of lets that clutch get to the optimum point of all this stuff.
I also go off of what guys say on here on springs to a certain degree and customer feedback is of coarse is paramount on all setups and how fluid things are when the engine goes thru the band. So many Guys ride so different its kind of a hunt to see what you really like and get the most out of forward drive and yet manageable for the rider. The wrong set up can just wear your az down and take all the enjoyment out of a long ride.
I know it sounds like a lot but you have to remember this is our drive system and its what makes us go good. JH