but you are not using "force" or "speed" variables.

What is the problem with your script ? is it not compiling or just acting strange ?

I don't know what your script does exactly, but I can say that you should do "thrust cap" after "raise thrust\lower" and not before.

If you just want to add this velocity limitation we talked about, try to add this after "--Movement RCS" block :

force = getCentralForce(Player)
speed = length(force)

if speed > maxSpeed then
    addCentralForce(Player, force*(-0.1))
end

you can try to normalize the force if the speed reach some amount :

force = getCentralForce(object)
speed = length(force)

if speed > maxSpeed then
    force = normalize(force)*maxSpeed
    clearForces(object)
    addCentralForce(object, force)
    -- you might need to do the same with the torque if you want to limit rotation speed too
end

or by applying an inverse force if you want it to be more smooth :

force = getCentralForce(object)
speed = length(force)

if speed > maxSpeed then
    addCentralForce(object, force*(-0.01))
end

do you mean like the object should behave normally with no damping but could not go faster than a certain velocity ?
or do you mean the object will be affected by a sort of resistance or friction ?