Sorry so tardy to reply Neil,
Here's what you may already have discovered:
The bulb housing rides in a tube which slides in and out of the back of the head. The purpose is to align the bulb so that it's spherical part mirrors the spherical section described by the one condenser. This is the only way to minimize light falloff at the corners. (I haven't found a permanent solution and am working on a diffuser to install later)
The head is designed to tilt 90˚ and focus on the wall for bigger prints. Weigh down the baseboard with books when trying this.
The column release is pressed in to loosen, and let go to set. The thread that attaches the head is 3/8 inch, and with a little widget from your local machine shop can be made to accommodate 1/4~20 (Camera Tripod size) and use as a copy stand.
Really an excellent machine.