I borrowed this idea from Wade Kloos used on his P-73 model. I used 1/8" dia. carbon rods in two places on each tip. The rod goes into the wing tip 1 1/4". I installed a 3/8" magnet just in front of the the front rod in the tank and the wing tip. I Installed a 1/8" dia. maget about a 1/2" behind the rear carbon rod in both the wing tip and the tip tank.

I haven't flight tested mine model yet but it works very well on Wade's P-73.