With regard to extremly pancaked bullets (soft lead like the dead center), this is what Al Marion has to say about it with regard to "Terminal Sectional Density", that article is here:

http://www.snipersparadise.com/tsmag/July03/july03.htm

Since the bullet will shoot thru both shoulders without fragmenting, there does not appear to be a problem with weight retention. Weight retention is the key to getting adequate penetration.
Anyway, your asking for "thoughts", that is what I thought when I considered them.
Chap