Okay got the art down pat for doing the plastic resonator clipped bundys, gee they are painful to remove the retaining spuds between shim adjustments. ...
That's one reason I don't shim pads on most instruments. Instead, I adjust key cup alignment.
".... Eg I had shimmed the key so that way just gentle light pressure in the centre of the key seals perfectly, however my daughter plays by laying her fingers on the hinge rods and gently rocks the key from the outer edge..."
IMO, it's time she or somebody got her to play the thing how it is intended to be played. She could also be setting herself up for RSI-type problems.
" ....I was using rolly paper to check clearances, which is about 1.5 thou thick, next time Ill have to find some material which is 1/2 a thou thick..."
Try video tape (mylar). It's just over 0.02 mm (0.0008"). Thinner if you sand paper off the coating.
1 thou is actually quite a significant leak. This can be ascertained by putting a leak light inside a sax, and closing a leather pad on translucent or transparent feeler of this thickness. The escaping light is what I would regard as a significant leak, even on a sax.
When a feeler is used to find leaks on a flute, very
light finger pressure is used, and the relative drag
on the feeler is what is detected in different locations around the pad. IMO this detects differences considerably smaller than the thickness of the feeler.