Thank you all for the responses and pictures. I believe I still prefer the strap slots below the battery tray, but I will give these a try. I was originally planning on just wrapping the straps around the battery and frame like with the E5s, but using the strap slots serves as a good place to store the straps
with the helicopter. On one occasion, I drove 18 miles to the field on a beautiful day and had everything ready to fly, only to realize that I left the battery straps at home. I am trying my best not to let that happen again.
This is what I have so far. This pic shows the straps on the heli in resting state.
This is a view to the inside of the battery compartment. Plenty of room for the 4,400mah and 4,500mah packs to slide in and out without interference from the straps. BTW, I use foam tape instead of Velcro on the battery plate. The foam tape allows for easy installation and removal of the packs, yet provide enough friction when strapped to prevent lateral shifting.
Left view with the batteries installed and strapped.
Right view with packs installed and strapped.
Bottom view of front pack strap. I really like how Matt designed the front of the battery stray with slits for the front strap. I also drew a line on the battery to correspond with the edge of the tray for perfect fore/aft COG.