Thanks Matt for the idea of using a 4-beat style.

I found a 4-beat style well suited for the 4-beat part of the song (_HOTJAVA.STY), then I selected 3-beat setting at bar 1, 4-beat setting at bar 11 and again 3-beat setting at bar 23.

It works well: BiaB changes the number of beats of the bars at the right moment, the style adapts rather well to 3-beat parts, and the arrangement is globally correct.

The only downside that I haven't been able to fix so far: the drum kick before the start of the song is still in 4 beats ... but that's a minor issue ;-) !

Lazy Bird