Actually I was going to span across my trusses with multiple 2x8's, then hang the track from that, so the track will be running parallel with the trusses, which are at 8' spacing. If I understand the clearances inside the track, I can then use carriage bolts from the track to a top plate which sits on top of the 2x8's.
This way the load is spread between my truss chords...theoretically giving each one only a temporary 250lb load which is also spread by the track supports.
I just don't see a great way to mount an I beam in the middle of the trusses since hanging it would require probably welding on some kind of bracket, which I could do, but for the light loads I'm talking about why spend the money on a beam when this track would give me over 2:1 safety margin. And it's presumably far less expensive.
Also been thinking about the vertical platform lift linked to in the post above. The biggest issue I would have with that is that I need to allow for something the size of a riding mower, so it would be pretty large. would need to be able to roll it off the lift so would need to extend the framework up probably 5' above the mezzanine floor.
Been trying to consider another method of doing the lift on vertical tracks, but keeping the winch itself anchored to the floor or bottom of the wall/framework and using a pulley at the top of the apparatus...but this would only be practical if I converted to a double cable setup so I don't have a singe cable in the middle of my exit area up top.
Would appreciate any other ideas!