I spent weeks dialing in smooth/fast realistic motion with Sim Racing Studio for all car classes (I own all content) using a single general motion profile. The only car that doesn't "fit" (output extremely jerky motion) is the X-17, thus unplayable. It looks like the physics/suspension on this bad boy might need to be revisited? Anyone else with same issue?
The fx17 is indeed on old physics and it's in the queue to be updated at some point. Expect it to feel more like the fr2 eventually.
The FR-X17 seems to do a lot of high frequency pitching at high speeds, which doesn't seem realistic to me. This may be coming through the motion rig. Maybe it needs a third spring like some of the other open-wheel cars do?
You are 100% correct... the motion rig abruptly and frequently pitches forward and backward. The Formula 2, 3, 4 don't have such problem. (FYI @Alex Hodgkinson)