Hi Comccoy, sorry I did not ans soooner. As to the length, what I did and not keep a record of is take measurements as best I could and then cut the rod about an inch longer than needed. Then I put it together and remeasured and than cut. If I were to do it again I would just use the whole rod and assemble everything except the small knob. Than hold the knob up against it, allow no more than 1″ of exposed thread when the vent is down and sealed and the rod is long enough to reach the other side of the knob, about another inch. Nick the rod to mark it, remove it and cut it to length.
The knobs don’t appear to snag on anything, but might depending on how frisky one is. What does appear to be a possible snag canadate is the setscrew I put in on one to prevent it from coming loose. Like Diving Duck the SS was a *^%#€ to drill in place and I was afraid to unscrew it using the glued on vent cap and not wanting to take a chance of the 4200 breaking loose. Again if I did it over I would have placed it in a drillpress not tried it in place. Another afterthought would be to make the rod long enough to extend past and out of the other side of the knob and then sandwich the knob between two locknuts, I think DD did something like this.
Bill