Been riding my kai zen twin trailer (which has a wing swallow like a spark plug) for the better part of a year, sporadically. Tim sold me NVS nautilus twins + trailer.
When discussing with him, he asked whether I'd be riding it primarily as a twin or a twin + trailer. I said twin +trailer. He moved the front boxes up either 1/4 or 1/2 an inch.
Since my first couple sessions, I couldn't get the thing to click with me. I felt it lacked drive... Like the fins were too far forward. However, I trust Tim's shaping more than my surfing, so I kept trying to make it work, but every session was the same lackluster performance.
I finally decided to test my theory, and I ordered the NVS kraken convertibles. if I couldn't get it to totally click after that, I had to unload it... And feel ashamed of my lack of rail surfing.
It clicked. 1/4 in made a huge difference, felt lots more drive, and got a feel for the rails as well. Left the session with a big smile on my face. Glad those fins exist.