You wrote:
"I don't make a "wye" style cable. I run a single 2 conductor shielded cable from the TRS to TS #1 and connect the shield and the tip lead in that one. Within that connector I solder a length of inshielded 20 gauge wire to the ring lead and heat-shrink it. This runs out the strain relief with the main cable, and solders to the tip of TS #2. It does not have any strain relief, but so far I have had no failures and everything has worked noise free."
I have to pipe-in on this... because I did this once and ran into problems... When I tried it, the client called me back and complained something just didn't sound right with his FX. He hooked up the beautiful new mogami snake I made, then he hooked up his old Radio Shack insert cables and my snake didn't sound as good. But, if you listened to my snake by itself it sounded OK, it wasn't until we made a side-by-side comparison that you could tell there was a problem.
The problem is the two conductors in most cables are twisted together, and the signal couples (cross-talks) from one to the other. There will be some time-lag though the FX unit and the "return" signal will be slightly out of "sync" with the send signal and this will cause subtle phase-cancellations and distortion.
I had to get another piece of mogami and rebuild the snake so the sends and returns were inside separate shields - you can buy cable that has separately shielded conductors (not twisted together) and that works too.