3 flow frames are 150mm
4 standard langstroth frames are 140mm (4x35)
Total width of your configuration would be
360mm
List of configurations here, although I haven’t got the 3 + 6 configuration, will add it tonight.
http://forum.honeyflow.com/t/flow-frame-fitment-in-langstroth-supers-metric/8575
-edit-
Just added the 3 + 6 configuration.