I'll try and make a stand, even though I'll admit I'm doing it tentatively, I'll say "Gravitational time dilation is associated with length contraction only in the direction of the apparent equivalent acceleration". There is no change to the width of the rocket or the lift (or whatever describes your non-inertial frame). The distance that the light beam has to go across the frame does not change but there is a change in the length along the axis describing the gravitational acceleration. Now how could we prove that? The other thing that has me baffled is that if Gravity is equivalent to upward acceleration (take the Earth ) 1 g. Now in space if something had acceleration equivalent to 1* g, it would get up to near light speed after a while, but the person on the Earth in the same equivalent acceleration is still locked on to the Earth, and hasn't moved an inch.