We are planning to do the exact same thing. We have dual tanks and I want to run one tank to the trailer for fridge
/ stove and one for our camp stove and a propane lamp.
They have y split adapters at crappy tire for $25 in the camp stove isle. They also have 8' extension propane hoses to get to your stove from the tank for $40. I think both are over the top expensive so maybe lordco has them for cheaper. If you do find them for a better price please let us know.
Personally I would not make my own, but I am a wimp that way =)