Best way to group scenes into chapters?

In my current novel, I have two interwoven storylines, back and forth, usually on a scene by scene basis. Each scene is posted here as TNBW chapter to make it easier to review. The scenes are named based on where I think they will fall in the published book (eg, scene 1.1, 1.2, ..., 2.1, 2.2, etc.). Since the storylines are mostly independent, with only occasional overlap, I decided to group the scenes based on chronology. Scenes that are closely spaced in time are grouped together, while larger jumps in time mark the end of one chapter and the beginning of the next. That has resulted in groups of four scenes, with minor exceptions. Unfortunately, my grouping method has hit a wall recently, with no obvious places to break between chapters. I now have up to eight scenes with no major jump in time. If I keep grouping four scenes at a time, I will be forced to split closely related scenes across chapters.

Suggestions?

Thanks
Dirk