See where you are coming from there and it does look nice.
Interested to see your results with it with regard to focusing. When shooting fly shots focusing has to be absolutely spot on, and the easiest way to do that is by enlarging the view in the LCD and then moving either the fly or the camera, 1 mm at a time, towards each other, then away from each other, while you watch for the sweet focus in the LCD. (Obviously you have to be able to take the shot without engaging autofocus when you fire it.) How does your rig fare with doing that? I kind of feel that making these microadjustments is easier with the fly on a clip (or the vice... or whatever), and the camera on a separate mount - whether it's a tripod (big or small), a beanbag, a macro rail, Scratch's ruler, a pile of books, or whatever. The other issue is lighting - I use 4 mini desk lamps, and any kind of rig would get in the way when I'm trying to crowd them round the scene - they even get in each other's way

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From a purely personal point, I don't like to photograph flies with a big vice head taking up half the frame

. Fly clips for archive shots, and free standing (or hidden prop) for arty shots
Sorry - that sounds like I am putting it down - not meaning to - more just commenting on the general area of photographing flies. I do like the look of it and if you are getting good results with it that is the main thing
Col