It's 3:00AM so I have to make this a quick reply and get home to get some sleep. I'd like to take the time to answer your concerns without sending you back into the thread but they have already been asked and addressed earlier in the thread, and like I said it's 3:00AM and I haven't even had supper yet. The only question you asked that has not been addressed is the possibility of rebuilding the vacuum pot. I haven't seen any posts of that portion of the DISA commonly failing so I haven't been overly concerned about it. If someone knows if the vacuum pot has a high failure rate, please jump in. I don't see any easy way to repair or rebuild it, so I think that would require a new unit which I would suggest upgrading with new valve internals even while it's new.
Thanks for your input.
"I'm a little rascal on my Little Rascal"