Zall,

1 rigid element that's length L and mass W works the same way as 2 rigid elements that's length L/2 and mass W/2.

Common practice here would be to split the element in half and put the support in the center and place a +Y with friction.

Though, you could probably just get away with the 2 +Ys with friction, too.

If two, forces from both supports are to be added together for purposes of structural design.

Make no mistake - the valve can rotate in the Z axis. The criticality of whether it rotates on the first support or the second support is dependent on whether the distance between these 2 supports is anywhere in the scale of the rest of the pipe.