I also use 4" white PVC pipe with test caps on either end.
1 1/2" open cell foam in the caps and the bottom cap is attached with 3 rivets.
Used a leather handle attached with rivets and use the handymans secret weapon (duct tape) to secure the removable end cap. I had no issues on my recent trip from Yellowknife to Eddies camp on the Attawapiskat. 2 jets, 2 cars, 1 truck and 1 float plane (one way) no problems. My stuff made it in both directions without being lost along the way too. I had 5 one piece rods, 1 two piece and 2 three piece fly rods in the tube, along with several hundred 3" twister tails to help keep the rods from shifting around in the tube.