MM wrote:

To avoid having to purchase a rivnut gun for just four fixings, is
there a kind of "rivnut" that has an outer thread as well as the inner
thread? That is, you insert the "nut" through the metal flange, then
fix it in place with a nut. Then fix the guillotine with bolts/screws
into the inner thread.

google for camera screw conversion bushes, e.g.

http://www.ebay.co.uk/itm/271019158544