In theory, the crank's stiffness (bending resistance) goes down with:
1.greater length (SB is stiffer than BB, other dims omitted, increased bore pitch)
2. longer stroke
3. reduced main or rod journal diameter (BBC rod journal)
When in doubt, larger radius at the journal edges helps.
I wrote some comments on journal overlap on my site: http://victorylibrary.com/mopar/journal.htm