I'm currently debating whether or not to email Florian Schlumpf and ask him if the Mountain Drive is Pugsley-friendly - I suspect not, since the Pug has a 100mm BB shell, but the only harm in asking is potentially to my bank balance
The current prize for Most Utterly Ridiculous Low Gear probably goes to a fellow of my acquaintance who has (or had, not seen him in ages) a Greenspeed trike fitted with, amongst other things, an SRAM 3x7 and a Mountain Drive. His lowest gear, with the MD engaged, was 7" ...