I re-terminated my T1's months ago using a standard 4 pin XLR. I used a standard soldering iron and normal solder. It worked just fine and has been working ever since, The solder flowed just as you would expect. I do not think there is anything special about the requirements to solder this mod. The entire thing took five minutes. In my experience the T1's benefit a lot from this mod if you have a fully balanced system.
That's good to know. My dealer re-terminated the T1 cable and adapter for me when I bought it but I've terminated some of my own with Cardas wire which was Litz (I made an extension cable for my T1 so now I can move up to 30 feet away from the amp if I need to. If the solder flowed for you as well as you say, then the stock cable for the T1 can't be Litz. This is a bit odd though because I know that the T1 cable is basically just a high quality stereo microphone cable repurposed for use as headphone cable and some of them are Litz as well.