Hi, Dena. Given that you have an Interstate GT, the B-van subforum
might bear more fruit for you with these kinds of questions.
A recent thread there called Two Way Refrigerator?
basically asks your same question and for the same reasons. It's a long read, but very revealing in multiple respects.
Edit: If you read that referenced thread, you'll notice that I started out being very pro-3-way, but evolved into ditching the propane refrigerator technology entirely (the thread transpires across multiple months). It was a real-time evolution of thought and experience that hopefully adds to the perspective that the thread has the potential to convey.