Ya 'Rapid rise.' Does anyone sell a 'slow rise'?

I put an MTB Deore-like Acera on the DownTube bike of a chum.With 20" wheels the mech looks dangerously low, but the bike never goes near logs, tree-stumps and so forth, so she is safe.

When Nexus 7 hub gears came out a few years ago, the MTB downhillers were all over them. 'Bullet-proof' they muttered, through mouthfuls of leaves and mud. They are now quite tempting, but a faff to retro fit.

Ooops.Way off-topic. Ignore my little rantings.