Thank you for those pics.
The center piece has 3 holes. Should mean that you can move it rearward in 3 steps.
Still need to remove some material from the center/motor bulk I guess?
It doesn´t seem to move the batterys to clear the center/motor bulkhead or am I missing something?
My LiPo tray does...

And my tray only shares one screw with the undercowl. So when you remove the undercowl the tray is still attached to the chassi.
http://www.tamiyaclub.com/showroom_m...08022010100048
I think this is one of few Tamiya options I will not buy.

Of course, they will maybe release an updated version of 511 with a modified/different bulkhead. Then this will fit without any modification.