I did't want to reply to my own question so editing the post .
It looks like editing the code is the way to do it . That's what i did any way . Besides i also have to now pass email from my custom sso besides having to edit code in
checkSSO() of net.jforum.ControllerUtils .
I found a bit of information from here :https://coderanch.com/t/578160 #19408 , its regarding redirects actually .
Also , every time i edit , i have to login again . If i haven't copied my post somewhere else , i end up typing it again . May be this is not the place to post it but is any one else having this issue ?