Takin' it to the E-side....

[Finnster]

Have you decided on the batt tray material yet? Let me make another suggestion vs alu.

I used UHMWPE (Ultra-High Molecular Weight Polyethylene, see item 4296A22 from Mc Master Carr.) A 12"x12" sheet is only ~$10. I orig did mine with 2"x2" angle to make lay-down style trays on ea side and it worked extremely well. The angle only comes in white however, but sheets are available in a number of colors (if you care.) The motor side was slightly wide, but this wouldn't be a concern in your case or by not using angle.

Not only inexpensive, the plastic is rated as "unbreakable" in impact tests, is easy to work (much like wood) and is light. 1/4" is recommended, but its half the weight of CF 0.91 g/cc (floats), so its no more than 1/8" CF (@ ~1.7 g/cc.) My two batt tray weigh less than 100g, and has lot of material to trim if I cared.

It can also be drilled and taped as well, and is pretty strong, but I used 4-40 standoffs (also from MMC) & flat head screws which fit perfectly in the 4mm mounting holes for the rx boxes/ gas tank. Its extremely strong this way, I could beat my trays with hammer and bend the chassis 1st I bet. with a little work, the trays would be trimmed to mount the chassis tabs flush for a smooth bottom as well.