Some Vixen dovetail clamps tighten without using a screw directly onto the vixen bar - I have a Geoptik vixen style clamp that I swap from various mounts. Although for holding something 10kg-ish, I certainly prefer a dual clamping Losmandy. Check out Testar's page of saddles....
https://www.testar.com.au/collections/dovetail-saddles