That's pretty much what you have to do. Put extension 10 on the w/bl and w/or and wire a jack to those pairs where x10 is going to be. Do the same with x11 on the w/gn and w/br and so on. Only problem is that you won't be able to do any more than 12 extensions ASSUMING all 25 pairs are cut through on all blocks which they usually are not. Normally you can count on three pair per line on the old 1A2 but that's about it. Like I say this is going to take some work.
-Hal
