Dave,

Making those decisions from the PCB design or stencil manufacturing side is 
really backwards.  That's really up to assembly engineerring.  The 10% rule is 
just a starting point.  And multiple CMs might want their own shapes, based on 
their equipment/processses.

We have talked about adding special stencils to our PADS library for years, but 
even with our own captive assembly, haven't come up with enough "standard" 
modifications to make it worthwhile.  We might do just a few that get modified 
the same every time.  The new mask adjust attributes Mentor added in v2007 
make it tempting for the PCB guys to engineer that, too, but that only allows 
for a same shape reduction/expansion.  They're probably most useful only for 
unique BGA, fine pitch, or via solder mask apertures.

Even a control freak like myself doesn't want to take on that part of the job!

Pete

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