I should try doing it the following way.
1) The stool should be physical for a real looking fall.
2) The stool can be held in place initially by either a hinge which you script to release, or by having buoyancy be 1 until released - then set it to 0 (or less for more drama). Or by having it not be physical from the beginning as suggested.
3) If the fall turns out not to be straight down, you need to have the stool run on a rail. That can be done. Drill a hole in a cylinder which will hold the stool, and stick a rail throug the hole. Make the hole approx. 30-40 cm larger than the rail to make up for the SL collision zone (or whatever it is). For a free fall I believe I would use a square rail and a square hole. There need to be around 50 cm of solid around the hole.
This means that a big part of the stool will be rail - and it will look mighty ugly. Make the rail and the tracker transparent, and make some nice looking stuff that can be seen.
Perhaps the tower itself need to be phantom to let the physical sizes fit as well.
4) perhaps there is a use of mega prims to make the tower big and nice in a few prims, one large collection is:
http://www.xstreetsl.com/modules.php?name=Marketplace&file=item&ItemID=701196Ahh, what have I been thinking, the tower itself is the rail, and there is one stool which is build around that - that should even look good.
If it makes no sense, please send me an IM, and I'll try to find you inworld.
-- Boreal