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Build Companion: Freewing Mig-21 80mm
Copyright 2016 by Brad Miser
Page 106
21.
Only two screws were used to mount the battery tray initially, but I used the two
additional screws that came with the model to increase the number of screws to four.
22.
Install a battery and connect it to the ESC and sensors. Make sure nothing interferes with
the battery going in or coming out. Also, make sure you can move the battery toward the
front or rear to adjust cg.