Yes i have some time again now a days to do things so ill try to get the pics up and a guide.
But yes it's the same procedure as mod 2 (2x 'christgift').

quick guide
Strip the battery's down, be careful when removing the top cover (connector on the battery), small shorts can accrue when doing this but as long as it is only for a second it will not damage the battery.
when both battery's are bare (don't need to remove the sticker/cover) put them against each other and tape them together.
Now comes the part where the soldering begins:
Take some wire and solder a long piece (5cm/2inch) this will be used to connect the + to + & - to - between the 2 battery's.
Make sure you make it as flush as possible as space is not in big supply in the battery space in the phone, USE CAUTION when handling the - on the battery's, solder only long enough to make the connection or you will ruin the battery, and also don't short it to the metal frame of the battery's since this is +.
In my dual japod config i used the connector from the very cheap battery from DX since it is very hard to take apart the japod connector.
To connect the connector to the new dual battery is pretty easy just solder wires to where the battery wires normally go. (or use B+ & B- markings)
I cut down over where i soldered the wires in the connector so that the wires took as up as little space as possible.
The bottom of the battery's has a thick plastic piece that helps to isolate the metal of the battery (witch is +) from the metal of the phone (witch is -), if space is very tight you can remove them and substitute with paper or tape.

Look to the pictures at post #2 for more help.
i hope this helps else please post and i will try to make it more simple or get more details on here.