FWIW,
When I set the float height on my Premeires I made a jig of sorts. I suspended a quart bottle filled with gasoline above my jig. I ran a piece of rubber hose from the bottle and attached it to a float bowl. I mounted the bowl at a 10* angle. I compared an old float and a new stay-up float. They both acted the same. The fuel level would be slightly over the edge of the float end farthest from the hinge. So I assume you can use the settings as recommenced by Amal.
Out of the box my Premeire floats were set even with the top of the float bowl, I believe Amal (or Bushman) says about 2mm down. I split the difference and went with 1mm. I did this during the winter and only got one short ride in, so I cannot give you too much info yet. Everything seemed fine after that ride.
Hope this helps,
Pete