Come on now, is it really worth the penny pinching to save your self a few bucks?? There is way more to diving safely than your rube goldberg contraptions. Even if you are vying for Darwin Awards, what about your family and loved ones? Insurance will likely not pay out either.
How Ken can say "there is no chance of over pressuring your lungs with this (see above) set" and still sleep at night is beyond me. How does he know? What if someone dies from using one of your contraptions? There is always the chance the idiot who uses your contraption will simply hold his breath from 12+ feet or god forbid the dinghy pump quits - god knows mine does from time to time, doing what it is supposed to be doing, or the battery dies while this same idiot is below or gets tangled in his hose or the boat bottom or gear.
I give up, trying to help people is getting more and more difficult every day, what with all the "experts" out there. Most of whom have never done a dern thing similar to what they suggest others do. I guess you can not protect people from their own ignorance. For sure - read a book by a reliable author or get some training, at least then you would have the facts, not some internet hearsay by an armchair moron.
And yes I am certified PADI, but that certainly does not make me an expert in any way.
Oh well,
dave