Soldering this thing together seems like a lot of extra work. If I was wed to the idea of having it "T" shaped like the store-bought jobs I'd probably make it with plastic pipe.
I threw my rod holder together in about 30 min once I got away from the "T" shape mind set. Rather than all those angles, I used a piece of thin steel strap, bent it to a "C" shape and fastened foam to the top of the "C" and the magnet to the bottom. Then a bungee to hold the rods in place.
The upper end is just foam attatched to the magnet with holes and slots cut into it to hold the rod tips.
As I write this I realized I could have done this much easier with aluminum strap.
Certainly not as good looking as Critter's but it works, & was cheap and easy.