Back in the late seventies I saw a t-shirt hanging in a boat dealership
“I’m not a Fast captain...
I’m not a Slow captain...
I,m a Half Fast captain...”
Other meanings intended by my screen name including another “projection” as possible Muslim (I’m not)in addition to what you suggest. Had it since ‘98, I typically use things till I “where” it out.
;)
So, I guess the shorter version of your moniker could technically be Fast, but even your "half fast" version is just a play on two words the second of which is not fast. It's a good one, I chuckle whenever I see it.