I was trying to figure out your 18x3, that I find a little bit obscure...but I remember to be convinced almost with the same idea: 6/4.
My original idea was (I write bass notes):
x x G x - x Ab x x - F x x Gb - x x E x | x x x x - x x x x
That is 4/4 + 2/4 drum fill.
But then, the drummer reharsing with me, pointed out that there was something more tricky, and asked to listen better.
We listened....and infact, the feel was that something was missing...
The ending E sounds like a beat 1, expecially because of the drum fill of 2 quarters, starting exactly on E!
That's why I ended up with taking out 2 1/16, making E the new bar start, becoming a 7/8 bar.
x x G x - x Ab x x - F x x Gb - x x | E x x x - x x x x
Anyhow, the drummer vision was totally different, not counting in beats but in tuplets....still have no idea how he feels it