I created this av-bay system for the nose cone on my 4-inch Mega der Red Max - a recreation of the Estes rocket.
It has a robust hasp for taking a shock cord (though the pictured attachment is just a leash - my cone is rigidly attached to the top of its body tube with 1/4-inch removable plastic push-rivets.
This system includes sleds for the EggFinder Mini GPS Tracker, the EggFinder Quark 2-event Altimeter, and the EggFinder TRS flight computer (which puts the GPS and Altimeter on one board). There's also a blank plug, which you can also use as a starting point for your own devices.
I've provided a cut-sleeve guide, for removing the original bottom of your nose cone, and a drill guide, for drilling your cone for the attachment screws.
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