the dm7 operates at 145 psi =10bars. I think this pressure is more likely for our work. I think we should have a look at automag styled bolts/valves as it doesnt stick and it cycles semi. >> 
 how much easier can it get:) I mean there are only 3 sliding/surface seals to be made. Someone might have already made it, as I didnt do any research in such a valve. But it for sure is different to QEV: 
btw I am not saying that this is how the dm7 works, rather it looks something like this: (too many seals for homemade stuff I think)



