Sorry to hear you are having troubles with Dave. I was new to sub modeling and I had a similar experience with Dave. He promised delivery within one week if I sent a Money Order overnite for a WTC 3.5. It took several months and much effort to finaly get the WTC. When it finaly arrived it leaked at the center bulk head and the gearbox is so sloppy the teeth do not always engage the way they should. The ballast tank vent would not seal and the tank would slowly flood. The gas saver had a bind and I could not get it to work reliably. I sent several e-mails no response and left two phone messages. No response. Several other people have had similar experiences with him.
Threats worked for me but I finally ordered a ballast tank and gear from Small World Models. The workmanship is excellent and everything works as advertised. And get this it all arrived on time as promised. David Manley is a class act. Other suppliers I have dealt with and would do so again are:
Skip at SubTech, Mike Schubar and Matt Thor. All were honest and helpful.
Don't give up and I hope your sub sails soon.