I thought my SID wasn't very stiff, but beats my old Reba from 07 by a lot. Don't notice a whole lot of difference between a '10 Fox 32 FIT RLC and SID. I ride the same stuff on both and don't think either has an edge. I did do a few trails faster DH on the Fox (not back to back, but on the Fox a year before), but I have a feeling that had more to do with tire choice than the fork. On trails I'm familiar with, they're both similarly capable, but the Fox's small bump sensitivity was horrible in comparison. I hear that the carbon CSU is actually flexier than alloy ones, but I don't think you have that model.
I do notice a difference between wheels and the feeling of flex. With CK hubs + Carbon rims, I expect rock solid stiffness, but I actually feel the fork wind-up more, leading me to over-correct with steering input when I don't get the response I expect. With a lightweight vuelta wheel from my old BD bike, it feels even flexier, but I expect it more and smooth out my inputs a bit and don't enter techy stuff so hot. About to replace it with a Tower Pro with 15QR (from reg QR), to see how things go. I like the control of the Fox at speed over the bump erasing abilities of the SID... sometimes feels like I'm running low on air with the SID, like an extension of my tire's suspension ability. Hard to gauge the feeling of stiffness by feel without taking into consideration all these other factors. If you measure by how hard you can attack the trail on a SID, compared to other forks, I'd say it is lacking, demanding more from the rider to be acquainted with specific nuances. I got used to it, but just not totally satisfied and wanting to try something else to see if I'm missing out, perhaps finding something to better suit me, my trails, and riding style.
