I did a search and did not find much. I have read through Hunner's write up, but he did not use a tray...
Did some work on the dual battery tray. In talking to other H3 owners who have already done this mod, it became obvious that the drivers side mounting tab of the lid seems to be an issue for everyone. It ends up under the fender lid, which makes it hard to tighten the bolts. I straightened the tray body tab to go straight up now and bent the lid lip to make the tab now go up, not out under the fender. This should allow me to install the bolts from the fender side and tighten the nuts above the lid. We will see if it works once I do the install.