A significant project for me was modifying a 45S head to make exposures more consistent. I would delay anywhere from a spit second to several seconds.
It's been described on this site in more detail. To make a brief summary, I installed a Zone VI compensating enlarger timer sensor and use the timer to make exposures. I purchased the last Beseler adapter from Calumet for a Zone VI Type II enlarger. For some reason, Calumet made this adapter about two inches thick. As a result, the 45S was floating about an inch away form the negative. (No good.)
So, I had an excellent, local, metal craftsman Cut it down to about 1 1/8" , the same as what they made for the Type I enlarger. It works great.