but 300mm isn’t that high to start with
Is it not?[/quote]
no not really, it’s a sensible middle ground kinda height, very adaptable to tyre/wheel changes in fact.
Don’t have exact measurements to hand but I know my bikes vary (currently and over the years) between ~10.5in and ~13.5inch, which is what 265mm to 350mm?
There can often be ~30 variation between models/brands of the same kind of bike so unless you were at the extreme end and thinking of going further in the wrong direction I wouldn’t be overly worried.
Also, think about tyre size, people have run anything from 1.8in to 2.4inch tyres on the same bike, that’s ~15mm just from a tyre change on the same wheels, so a bit more leeway in either direction isn’t a big deal.
Add to that the fact that a smooth trails/moorland wanderer will get away with a lower BB than someone who regularly has to pedal up and along deep rocky/rutted type trails and you can see that ‘optimum’ height isn’t a static thing
People get far too hung up on BB height, especially on HT/rigid bikes, unless you’re talking right at the extremes of height, extremes of terrain, or extremes of performance then it’s into the realms of insignificance.
I say crack on with your experiment (whatever it is) and have some fun 😉