Personally, I don't understand the concern with storing the trailer in the UP position, as long as it's not moved. Yes, there is tension/stress on the cables and pulleys, but it is static tension/stress and not dynamic tension/stress which could cause metal fatigue and possible failure over a very long period. So, my answer is nothing will happen, as long as you periodically (maybe once a week) activate the lift mechanism to raise the top off the safety bar which it MAY have settled down onto. I think prolonged weight on the safety bar can deform it and cause it to fail. I think the cables and pulleys are strong enough to support the top, especially since they are only supporting about 1/4 of the weight, each.
If there are concerns, simply cut 4-2x4s that are just long enough to insert between the outriggers and the top, so that the top is supported by them, rather than the cables/pulleys or safety bar.
But, if the trailer is moved, lower it first! Movement will cause large dynamic stress on the entire lift mechanism, as well as possible twisting forces on the guide blocks which could break them. The dynamic force changes on the cables could also cause damage to the points where the cables are attached to the top, possibly loosening the bolts there or causing the cables to "cut" into the lower edge of the top.
- Jack