Hi greaserig.
I don't know if TheVictim still frequents this post, but I'm interested in the whole sterling side of things. I'm not sure how he will connect the whole lot to the diaphram, or what sort of rpm TheVictim will get from his sterling, but I do know on your genny side you need quite a bit for useful single phase power, at least 3000 to 3600 rpm, and then you need some decent magnets and coils too.
So he might still need some gearing to get it up there.
Further, running a sterling at that low temp sounds risky, what I've seen is motors running 200deg.C plus to make max use of the air inside the system, and that will give your diaphram idea the march.
So it's back to a solid material design and flywheel setup, or so I believe. The flywheel can have some particular benefits, but I agree with him, you need more that two cylinders.
Is there someone who have actually built a successful sterling on the forum? Maybe he/she can give us better pointers in this regard.
I've been toying this idea for very long, and have done some design along the lines, but buying the materials to build all is a pain, and it's going to be an expensive exercise.