MTU help

Hi all,

I need some assistance with a performance issue we are having.

We have 2 MT’s RB230’s in production bridging 2 networks.
Basically exactly the same as described in this article.
http://www.mikrotik.com/docs/ros/2.9/interface/eoip
down the bottom example.

The only difference is that both Internet links are done via PPPOE.
So the MTU is set at 1480 for both Internet links.

Does anyone have a recommended MTU set for all the interfaces listed ?
ether1 1500
ether2 1500
pppoe 1480
pptp ??
eoip ??
bridge ??

My current settings just do not have the thruput and the routerboard gets hammered 100% cpu.

Thanks in advance.