NEC 250-24 (a)1 says the the connection has to be accessible. The meter seal is interpreted as not readily accessible around here.

From a circuitry standpoint, bringing the GEC to the neutral on one panel (#1) provides the fault path to ground for both panels (#1 & #2). The NEC minimum is that the GEC connect to the neutral bus in panel #1. I'd worry that the service neutral terminals between the disconnect in panel #2 and the meters might fail at some point resulting in the possible floating of the grounded conductor until the problem is corrected. There are probably going to be a few inter-connections between the groundING conductor webs of dwelling #1 and #2 that will then be carrying panel #2's neutral current [Linked Image] and MAYBE some parallel paths off #2's groundING conductor web to ground will help, but I'd rather not accept that liability.

I like adding a GEC sized for the capacity of panel #2's service conductors (in this case the #3) connected between the neutral buses of panels #1 & #2.

Al

Al Hildenbrand