Note: I don't like to modify OEM parts so I ordered a cheap, opaque-black replacement cover to make my prototype.
I tried to upload some photos but received a "server error" that I couldn't upload more than 146Kb, even though my photos are smaller than that. So here's the procedure I used to convert my Dark Fire to use a different battery.
First, the LPE8 charger tray needs to be trimmed in order to fit in the available space. Then wire the tray to the 3.5mm jack with the normaled switch. Wire the other side of the switch to the CPU using a "ZH 1.5/3P" connector. (aliexpress) Because the ZH 1.5/3P connector could be plugged in backwards, the CPU is labeled showing how the red & black wires should be oriented. For the 3.5mm connector, I drilled a hole in the lower right corner of the replacement cover as there was an empty space there in the control cavity.
After drilling holes and screwing in the brass inserts, holes were drilled in the replacement cover for the thumbscrews. The thumbscrews hold the cover securely, but if the need arises to swap batteries in the middle of a long gig, (like when there isn't enough time to use the charger plug) the thumbscrews allow quick & easy removal/reattachment.
I ordered 2 sets of the LPE8 battery/charger combo... one to modify the tray for use in the cavity, as well as to fashion a "pluggable" charger. The other LPE8 is used as designed to charge the second battery.
I'm happy with how the project has turned out. The only other thing I might end up doing is to order a sheet of smoked, translucent plastic to fashion a replacement cover that more closely mimics the OEM. In the replacement cover, the holes where the original wood screws held the OEM cover in place are still there and visible. Also, there is a Gibson "G" on the CPU that glows when the power is on... I wouldn't mind being able to see that again. 😉