CAKE settings for "IP Passthrough" (not bridged)?

[hifiwifi]

Running my RT-AC86U with a BGW210-700 modem (ATT DSL). The modem does not offer a true bridged mode, but it does offer "IP Passthrough," which seems to do the same thing.

My question is which of the CAKE "WAN Packet Overhead" and Mode (ATM/PTM/Normal) settings would apply here?

On the modem admin info, it is reporting as a VDSL2 connection.

 

[hifiwifi]

Here is the biggest packet I could get using the ping method. Is 28 then the correct number?

$ ping -c 3 -s 1472 yahoo.com
PING yahoo.com (74.6.143.25) 1472(1500) bytes of data.
1480 bytes from media-router-fp73.prod.media.vip.bf1.yahoo.com (74.6.143.25): icmp_seq=1 ttl=46 time=73.9 ms
1480 bytes from media-router-fp73.prod.media.vip.bf1.yahoo.com (74.6.143.25): icmp_seq=2 ttl=46 time=71.6 ms
1480 bytes from media-router-fp73.prod.media.vip.bf1.yahoo.com (74.6.143.25): icmp_seq=3 ttl=46 time=73.0 ms

 

[sfx2000]

With most VDSL2 connections - I would suggest 34...