I can only really comment on the equipment I have and use - What I can tell you about the spring is it damned strong and you do not want to get your fingers caught up in it (it hurts a lot !).
Should you need to change the head, either use a strap to hold the carriage down or raise it to the top of the column first.
What Paul said is very true. My painful experience was when I was adjusting the head down to transport the 1200. Wow, zingo and the tips of two fingers got a bit mangled with a disproportionate amount of pain. The spring is a monsta and it's great using it's well balanced strength in the darkroom but it sure can bite if rubbed the wrong way.