Good Afternoon, Jeff,
I agree with Michael; it takes just a couple of seconds. Using the enlarger in this fashion, however, does have some complications. It is critical that the wall surface be precisely parallel with the enlarger lensboard and the negative carrier. The tricky thing is that both horizontal and vertical axes must be trued up, with horizontal being the trickier. I never found the effort involved to arrange everything properly worth the bother. On the few occasions when I've had to make an oversized print, I moved the enlarger forward, clamped the rear of the enlarger (very firmly!) to the table, removed the enlarger baseboard, and projected downward between the metal "legs" onto the floor. If you frequently need very large prints, it would be worthwhile to build an enlarger table with a removable center section.
Konical