okay. let's give this a shot.

utils/he_ipv6/tpl/radvd.conf.j2

@@ -1,30 +1,44 @@
-# Generated by he_ipv6
-{% for assign in assignments %}
-	{% for assignment in assign.iface_blocks %}
+{%- import '_common.j2' as common_opts with context -%}
+# Generated by he_ipv6.
+# This may go wonky with multiple assignments on the same iface.
+{% for assignment in assignments %}
 interface {{ assignment.iface }} {
 	AdvSendAdvert on;
-	# Is it 1480 or 1280? Arch wiki says 1480, but everything else (older) says 1280.
-	# AdvLinkMTU 1280;
-	AdvLinkMTU 1480;
-	MinRtrAdvInterval 60;
-	MaxRtrAdvInterval 600;
-	AdvDefaultLifetime 9000;
+	AdvLinkMTU {{ common_opts.mtu }};
+	MinRtrAdvInterval {{ common_opts.min_inter }};
+	MaxRtrAdvInterval {{ common_opts.max_inter }};
+	MinDelayBetweenRAs {{ common_opts.min_delay }};
+	AdvDefaultLifetime {{ common_opts.lifetime }};
+	{%- if assignment.ra_dhcp is true -%}
+	AdvManagedFlag on;
+	{%- endif %}
+	{%- if assignment.ra_other is true -%}
+	AdvOtherConfigFlag on;
+	{%- endif %}
 
 		{%- for block in assignment.iface_blocks %}
 	prefix {{ block|string }} {
 		AdvOnLink on;
-			{%- if block.prefixlen == 64 %}
+			{%- if block.prefixlen <= 64 %}
 		AdvAutonomous on;
 			{%- endif %}
+		AdvValidLifetime {{ common_opts.lease_life }};
+		AdvPreferredLifetime {{ common_opts.lease_life }};
 		AdvRouterAddr off;
 	};
 		{%- endfor %}
 
-		{%- if ra.dns is true %}
-	RDNSS {{ nameservers[assignment.iface]|join(' ') }} {
+		{%- if assign.ra_dns is true %}
+	RDNSS {{ assignment.iface_ll }} {
+		AdvRDNSSLifetime {{ common_opts.opts_life }};
+	};
+		{%- endif %}
+
+		{%- if assign.ra_domains %}
+	DNSSL {{ assignment.ra_domains|join(' ') }} {
+		AdvDNSSLLifetime {{ common_opts.opts_life }};
 	};
 		{%- endif %}
 };
 
-	{%- endfor %}
 {%- endfor %}