Back in stock.
Tray is attached using the same holes as the original battery posts. No need to modify the chassis. You can also use the original battery posts and battery plates. The cradle is 69x47mm, so most saddle pack lipos fit.
The tray also fits the 511, but please note that you will have to remove some material from the center bulkhead in order to fit a LiPo.
I also have a 511 LiPo tray that moves the LiPo back ~4 mm to clear the center bulkhead.
Slim design fits both 501X and Azarashi body.
2 Piece tray is made by Fibre-Lyte in 2.4 mm carbon.