Here is very demonstrative sample showing the scale issue.
http://arkeon.dyndns.org/scol/physicscale.rar
(compiled with newton dlls in debug)
The box on left :
- ground have a box shape and is scaled.
- the spheres on it have continuous collision enable.
- each sphere have a different initial size and is then scaled
The box on middle :
- ground have a collision tree shape and is scaled.
- each sphere have a different initial size and is then scaled
The box on right (1:1 for reference):
- ground have a collision tree shape with no scale (1:1 ratio).
- each sphere have no scale (1:1 ratio).
all the spheres have the same mass and size, and no special material used.
the sphere diameter in world is 1.02 meter.