RE: stuffing tube
I'm running the stock Mean Machine collet on an OS 18CVR-M connected to a Prather 3/16" flex shaft running in a 1/4" OD brass stuffing tube with no problem so far in my MM hull. I check the tightness of the allen screws on the collet when I grease the flex shaft after each days running.
I converted my MV v1 to a .150 Aqua flex shaft running in a brass tube. I usually run the Aqua .18 with a 2.5 tuned pipe but have also run the OS 18CVR-M in that boat with zero drive line problems.