I have done exactly the same honing the underside of the cap iron to all of 
 my re-commissioned Stanley bench planes, following the written and 
demonstrated  procedures advocated by David Charlesworth.  As a result of this 
careful  approach, I've not had a problem with shavings getting under the cap 
iron.   Nil.
 
Also, as advocated by Charlesworth, I have re-shaped the top side of the  
cap irons by making the round steeper, and then polishing them to 8000 and 
steel  wool with Simichrome.
 
So, I could put these puppies in a jig and hone a high-angle secondary  
bevel on the top side leading edge of the cap irons, what is the thinking of 
how  high an angle that secondary bevel should be.  BTW, out of ignorance I  
suppose, I've always been in the school of setting the cap iron very close to 
 the edge of the blade (less than 1/16th inch).  I have no complaints about 
 how the planes work (I've put Hock blades in all my bench planes), but if 
I can  wring a bit better performance by the new approach, I'm game to try.
 
So, what angle secondary bevel would Ya'll suggest for Stanley cap irons,  
given this new approach?
 
Cheers,
John
 
John M. Johnston
"There is a fine line between hobby and mental  illness." Dave Barry  

oldtoolslist@g... writes:
 
For many  years I have honed the Stanley cap iron underside to a slight 
angle where it  meets the iron to be certain that it contacts the iron at the 
very tip. This  prevents shavings from lodging there. I also have been honing 
a 45 deg.  secondary bevel on the top side of the cap iron, but now I see I 
need to go to  a much higher  angle.

------------------------------------------------------------------------