Ok I took the top off, double checked float level and float drop. I made some minor adjustments for both. Put it back together and it's still leaking. I don't know if I said this - but it doesn't happen at idle - only while I've driven. That's why I'm sure the fuel is rising up and sloshing into that channel.
I think I found what might be the issue. The kit came with three different needles. I used the short one from what I read on the manufactures website. However I may have just misread something (as I do). I just read a thread on the exact same issue I have - the problem was resolved by using the needle with the little spring button on it. (see photo)
I'll take it apart again and try the springy one, and report back.