Changing roller size.

[A440A@AOL.COM]

Jim explains: 

<< All other things being equal,  a 
smaller knuckle would  require a higher capstan to get the same hammer 
line,.... but since we only changed the roller/knuckle the key must move 
further to reach letoff and it is this addtional key travel that produces a  
higher catch point for the backcheck. >>

  Oh,  ok, if you change the knuckle and don't reregulate, then the 
difference will extend to virtually everything.  However, if you decrease the 
knuckle size, and re-regulate the action's hammerline, let-off, drop, and 
spring if it needs it,  I don't see the difference in diameter changing the 
backchecking.  
Regards, 
Ed Foote