Long story short - Rockwell sent me a replacement 6S handle because of some issues I was having with mine. Rather than throw the old (and faulty) handle in the trash, I decided to grab a cheap Signature Shaving Co. head off of ebay to use with the old 6S handle. It... did... not... fit. It tried to cross-thread almost immediately upon attempting to mate the pieces together.
But I was not to be deterred. I grabbed my wife's rubber oven mitt for extra traction, and I cranked the Signature Shaving head all the way down onto the 6S handle. It was nearly impossible to remove after doing so, but I was able to remove it and repeat the threading procedure several times until everything loosened up. Now the two parts fit just fine, but I fear I've ruined both of them for any other future mates. Haha.
But I was not to be deterred. I grabbed my wife's rubber oven mitt for extra traction, and I cranked the Signature Shaving head all the way down onto the 6S handle. It was nearly impossible to remove after doing so, but I was able to remove it and repeat the threading procedure several times until everything loosened up. Now the two parts fit just fine, but I fear I've ruined both of them for any other future mates. Haha.