Thanks for suggesting those battery trays; they look nice. I might have to get the Tekno one later. For now, I'll just add some more velcro and another angle bracket at the front, then see how that goes.
The battery is from
Efuel Hobbies. It's only 16C/80A, but it was a good deal when I got it - brand new off eBay for less than $90. As long as I don't go crazy with gearing, I should be fine. Right? Sadly I don't have the equipment to know the amp draw on load, although I find that the ESC, motor, and battery are not running hot after about 10 min. of run time.