Is prefix delegation not supported on the cga4131com?

Am I barking up the wrong tree trying to get this to work?

I have a /29 block of static IPs so am using the modem in pass through mode, not bridge mode.

Edit: After putting the cga4131com in bridge mode (using dhcp ipv4 wan as required) prefix delegation works instantly. This is a breath of fresh air after a demoralizing few days trying to get pd working through pass through mode with zero success.

Edit2: But really, it leaves the question is ipv6 functional with static ipv4 or do I need to choose between them?