Interesting project. You don't need to worry about the bulk of the phantom blocking the gps signal. They even work when installed under a car (have done a few hundred installations myself). As long as they are not closed inside a thick metal box, they will work fine.
To make sure it will work fine even after a crash, you can wrap the unit with a few layers of bubble wrap. A few months ago we had a client use his 102-NANO to locate his meteorology balloon. With plenty of bubble wrap the tracker survived after 500m+ fall.
I have noticed you haven't used the waterproof pouch. The tracker itself is not waterproof unless used with the waterproof pouch supplied.
