So just to confirm, the chrono functions work? ie: does the 12 hour counter also move or is it like the Omega speedmaster that has the 12 hours counter stopped at 0?
I am no expert on Speedmasters, but to my recollection most have all subdials functioning. The real issue with speedmasters is the spacing of the subdials. I have never bought one for that reason. There are probably some speedmasters where they froze 1 or more of the subdials so they could put them in the proper place & maybe that is what you are thinking of.
Any issue that you are going to have with a chronograph is the following. With the exception of the 4130 Clone for the Rolex Daytona there is only an A7750 at this point that the rep makers use for Chronos and the native or way it was designed is to have the position of the second hand subdial @ 9. If the Gen has the sec @ any other position than at 9 then they have to add some gears to get it to where ever they want it and then it adds height to the watch and if there is a date wheel it makes the date look sunken. The experts all agree that most of the time moving the sec subdial away from @9 also causes other issues that increases the chances that something might go wrong, especially when it comes to the chrono function.