Unfortunately I didn't have the measurements I though I did, sorry! That link above is useful though - the top of the tube (in charlie X) is about 6' off the ground and the bottom is about 2' - leading to an approximate diameter for the tube of 4', not 3' (as the Season 2 setplan shows). I always took the setplans as correct, but the screencaps do not lie! (see also http://tos.trekcore.com/hd/albums/2x...abelhd0472.jpg
for a shot from Season 2)
The steps appear to be about 1' wide. The initial block is about 1' high and 6" deep.