In reply to Fredt:
Used flexible 12 point crampons (straps) with my Mescalitos, without any problems.
My rule of thumb is that it takes about two grades off my ice climbing grade.
Conversely the Mescalito climb two grades better on rock than the B3 boots I have, so your suggestion would probably be my first choice as well, assuming you mean the Hornli. (Probably 90% rock in September)
Best to try the combo out somewhere first. A steep grass or clay slope convinced me they were staying on the boot.