Thanks Jipe. Interesting points. Maybe i should give a Brompton more time. I don't have much experience of riding smaller wheeled bikes so your insight is appreciated. I guess with lower weight and radius smaller wheels are easier to accelerate, an advantage in stop start riding. Larger wheels take more to get going but maintain more momentum and provide more stability (relatively) at speed?

The relative lack of top notch tire choice in ETRTO 507 is a downer.

Are SS frames not still heavier than Ti equivalents?

Helix does have mounting points on the steering tube and we've seen a design for a universal mount that appears to allow full steerage inspite of the fork design. Clever fender and rack designs too which work with the fold. Designs only so far.