Ooh, sounds like a challenge to learn proper skills Alan-
Not having the time or inclination to do that,
and not having access to numeric control, other than my own digits,
I'm afraid I have to design within the limitations of what I can accomplish myself-
I suppose I could farm bits out, but it can get expensive,
and there's usually another way to do things.
Perhaps not the best way, but it gets things done.
The back-
yes, that's a weak link- in one regard, it's less than a positive lock.
On the other hand, it's an advantage-
having literally nothing holding the backs in place is a lightweight solution,
and keeps the form factor to the minimum dimensions possible.
This camera was designed to be hand held,
so just holding the camera keeps the back in place.
That, and friction- the back is rebated by 5mm, and it's a tight fit.
I've used it with the 545 back pictured, a Polaroid 550, Horseman 6x9 and 6x12 roll film backs, and an assortment of 4x5 film holders.
Of these, the newer 4x5's, the Polaroids, and the Horseman 6x9 backs are a perfect fit, and are gripped just enough.
The 6x12 back is slightly larger, and is a tight fit, but works. I don't like using it though,
in case it stresses the camera, and stretches it.
The older 4x5's are slightly smaller, and wobble-
one of them is much too small, and fell out the first time I used it.
A metal tabbed Lisco Regal. So they don't get used anymore-
It isn't a perfect solution, and is open to criticism,
but since I'm the only one using it, it suits me just fine.
the interior rebates are lined with velvet tape around the edges...
I also made a ground glass that mounts like a film holder, for critical composition-
but it kindof defeats the point and shoot idea-
I've shot quite a lot of film with this camera in its previous iteration-
with a plastic 50mm lens-
you can see some of them on my flickr-
they're most of the recent ones-
http://www.flickr.com/photos/joseph-jb7/
I could have used a graflok style back,
but that would have made the camera much bigger,
and much less of a point and shoot.
The next one will have a proper back, along the lines of this one, but smaller-
http://photographyireland.net/viewtopic.php?t=25732