having watched some videos on YouTube it appears to be a 60/40 split so I won't bother with the 40/20/40 split.I don't think that's correct - certainly looks 60/40 on review videos
https://www.youtube.com/watch?v=Ws8LEPPNo28 - pause at 5:05
https://babybmw.net/forum/viewtopic.php?t=135064
This topic suggests it's 60/40 standard too.