355 Spider Seat

I'm sure this issue has been addressed somewhere I just couldn't seem to locate the relevant thread. The driver seat on my spider 355 feels like a rocking chair....Well you see a fellow chatter that I bought the car from was a bit oversized, hehe, he’s gonna kill me....well I'm sure this can't be the actual cause of the problem, but I tried fiddling around with the circled parts in the pic attached and wasn't very successful. Has anyone experienced the same problem, or any clues as to how it could be fixed?
Anyone know where I can find used Spider seat?
Another thought, has anyone changed their seat belt color….I wonder how a red seat belt would look on a Red F355..
Image Unavailable, Please Login

 

Great thanks ! Ok I'm trying this :
"Next, check your seat back positioner. Tilt your upper seat beat all of the way forward, then all of the way back, then set it to your preferred angle and verify that it locks in place. Thanks, No Doubt"

Here's the issue, my seat positioner goes up and down but the actual seat postion is locked and will not move ? Should I take the whole seat out ?