Sorry for this late reply but have you tried looking at other topics and resources to help you with problem you are having? - I have looked into other topics and it seems as if you will need to turn this into a whole cframe and then clamp like so:
local ConstructCFrame = CFrame.new(rightShoulder.C0.p) * CFrame.Angles((rx)+ math.rad(115),0,0) * CFrame.Angles(0,0,-ry+ fy)
local OrientationX, OrientationY,OrientationZ = ConstructCFrame:ToOrientation()
local MinLimit, MaxLimit = -.8, 50
local ClampedAxis = math.clamp( OrientationZ , math.rad(MinLimit) , math.rad(MaxLimit) )
local NewCFrame = CFrame.new( ConstructCFrame.Position ) * CFrame.fromOrientation( OrientationX , OrientationY, ClampedAxis)
Oh how great I forgot about object space when I have a script that uses it for character rotation as well. I still made some mistake on my showcase so if you want to use I or anyone I will fix it to accommodate for the errors.