bigmagoo,
to save trawling through the whole thread.. I’ve tested it, as has Chris with several BB heights.
Based on my past experience with LT and slack 29ers and designing the Ion15 I expected taller BB height than the 27.5 with 29 wheels to facilitate side to side manoeuvrability and aid braking weight transfer.
Chris convinced me not to do that initially as he reckoned the BS BB (335mm0340mm) the same as the 27.5 would be the daddy.
So I was riding with the lower BB (It is easy to configure with 1 or 2 bushes, depending on preference) and switching between the 29 and the hybrid. I found I was having to steer the 29 at the rear with my hips in tighter corners and initiating turns and wasn’t keen on that. We tried messing with the suspension/rebound trying to find something to take the feeling away. I even wondered if it was to do with the oval ring.
I then decided to revert back to the higher BB at 350mm. It was a transformation, much nicer, more neutral feel all round, I didn’t feel it was hard to get stopped and never gave the side to side agility a thought.
As mentioned by Shandy, Chris and I think this is a lot to do with the dynamic ride height and the steering axis. No definitive answers but the result of the higher BB for me was a 29er I enjoyed riding rather than one that frustrated me.
The GeoMetron does sit into its travel and then hit quite firm support at the sag point.
Interestingly 350mm delivers the same BB drop as the 27.5 version.
Summary is if you want to drop the BB you can get it to 340mm in 155 travel setting. That low isn’t possible with 170mm rear travel. you can deliver 350mm with the 170mm.
In terms of will the geo change. If I was being picky I’d increase the SA to 78deg static, but it would make no difference in the real world.