extra heavy duty jack stand

[Frank S]

Nice work Frank. You should slot those holes a bit, then put a second set of slotted holes 90 degrees out. That'll let you put a second pin in, perpendicular to the first. Lift it half an inch with the slotted hole but keep it pinned, then put the second perpendicular pin in. So there's always one pin holding it and it can never drop very far. Keeps the blood blisters off your thumbs.

I mainly built it to have a stable platform for a hydraulic jack on top of it while needing to unload the suspension on a vehicle for adjusting the caster or camber

If I was to build a second one to have a mated pair for use under say a medium sized dozer or under a Semi tractor or trailer then I would most likely add more holes in the outer tube at differing heights to take advantage of smaller height adjustments, by simply raising and rotating the inner stem. Slotted holes don't do anything for me as to make them effective I would need to drill a complete series of holes in the inner stem offset like you mentioned to be able to lift while pinned to place a pin in the next higher hole 90° off