I do realize that the rear shock is a piece of crap.and ohlins are expensive. 04 to 07 forks would be dandy..Mostly concerned about rear.was thinking about swapping the rear spring progressive springs are real soft for the first bit .take the bumps better .thats what i think .. ????????????????????????????
That spring change might help a tiny bit...but, it's the RATE of compression in the valving that is the real problem. Softer springs don't address that too-firm-compression valving. IOW, it's not the spring that is kicking you in the rear when you hit a sharp bump, it's the stupid valving compression rate that's kicking you in the rear.
On top of that, the rebound is way too slow...so the rear wheel skips once it's kicked up in the rear. Worst of both worlds. It's very dangerous to ride this bike hard in corners that have sharp undulations. I almost dumped it the first time I hit a particular bump, because it kicked me, then hopped and slid a couple of feet to the outside of the turn. That was at about 45 mph. 40 mph is about the maximum I could ride that particular section on the stock setup, and not be in danger of losing control.
I bought a used OHLIN's rear, did some recommended adjusting to the front (I have an 07), and I can now go through that turn at over 70 mph with more control than the stock setup at 40 mph. I would have sold the bike if I didn't find a solution like the OHLINs provided. My slug KLR650 was more fun to ride on the road than my 919...as the KLR had front and rear suspension upgrades, and even with dual-sport tires on it, it would out-corner the 919! Not only that, the KLR was SO MUCH more comfortable.
The people that did my KLR suspension would have considered doing the 919...but, judging from the lack of a market for 919 upgrades, they aren't going to fool with the 919. It's a business decision based on R&D costs and return on investment. As a GROUP, 919 guys just aren't very savvy about suspensions. Don't get me wrong, there are some GREAT suspension experts regarding the 919, and I'm NOT one of those experts...nor will I ever be. But, I do know what doesn't work well, and that's the stock rear shock. And, I know changing the spring rate isn't addressing the real problem...which is the valving rates.
Oh, and I also know the Ohlins saved me from selling the bike. I say save your money instead of chasing a different spring rate, look for a new or used Ohlins, or, see about getting someone to change the stock valving for you.