Yes, these adapters do work very well ....with much lighter 'stills' cameras - but don't know if I'd trust one with a much heavier 16mm Eclair.
If you must buy one, go for the ( more expensive ) Arca-Swiss adapter. This is probably made of better quality hardened steel ( as you'd expect from Arca-Swiss ), though personally I'd ask them first !
I have had one of the cheaper ones break on me, due to ( my excessive ) force.
One other important thing, check the Eclair's base will safely take the 8mm depth required without causing internal damage.