Yes, the S42 tube should fit the S43S.
Here's my S43 sporting the SS bezel and body of the S42S
That looks like a nice setup!
I have this light. Although its cool looking the beam pattern is horrible. In comparison to the quad IF25A, the latter is so much better. Also, its the hottest running light I have and I have well over 100.
I got a few light on my shortlist, that Sofirn is on it for sure