Thanks, Klaus:
I tested it with voice/headphones and switching polarity, and the back capsule has slightly nicer bass. I have heard that capsules can lose some bass response after 40 years of use, and I thought the front capsule in cardioid probably got more use than the back one in Fig. 8, hence the reduced bass response. I thought if one could easily switch them I could use the back capsule for cardioid, and they would be perfectly balanced again in about another 20 or so years.
Thanks for your thoughts,
Stephen