Since my most recent post we have tested the new SNPs in many different I-M26 people from all the major subgroups. All were L673+ and L707+ so I think L673 and L707 are equivalent to M26. (It's possible that these SNPs and L158 and L159 are actually above M26, not equivalent. But the other major groups of I-P37.2 are ancestral (negative) for all these SNPs, there are a few small groups who have not tested all of them yet).
L672 is more interesting, some I-M26 people are L672+ and some are L673- which introduces a new level in the tree. It turns out that all the people with YCAIIa,b=11,21 (or who are close matches to these people even if they have different values) are L672+. The people who are expected to test L277+ are L672-, and these people have YCAIIa,b=18,21 and are quite different in all their markers from the L672+ people. (L277 is placed in quotes because Family Tree DNA cannot make this test work for L277+ people, but we have results from 23andMe).