Got it..  I reverse engineered a prop file and figured it out.

to turn it off:

actor hip
{
off
hidden 1
castsShadow 0
includeInDepthCue 0
visibleInReflections 0
visibleInRender 0
}

to turn it on:

actor hip
{
on
hidden 0
castsShadow 1
includeInDepthCue 1
visibleInReflections 1
visibleInRender 1
}