Transparent site to site - DHCP confusions

[hardware_failure]

I have a transparent open VPN between 2 sites.  It works wonderfully for allowing both offices to think they are are on the same network.

I am having a problem with DHCP however.

I would like Site A to use its own DHCP server.
I would like Site B to also use its own DHCP server (pfsense)

The main reason for this is for each site to use its own gateway for obvious reasons.

The problem is, clients at Site A sometimes pick up the pfsense at site B's DHCP. (bad)

I have tried creating a rule to block any any any etc on ports 67-68 on all but the LAN interface, but that didnt seem to help.  Maybe because of the VPN being "transparent" its still able to reach site to site via the LAN interface?

Any help / feedback is greatly appreciated.  Thanks!