Yesterday I took a look at a mountain bike (parked in the basement at my work) set up with one-handed controls.
Clearly, some of this will be irrelevant if you're considering a bike with dropped bars, but here goes anyway.
Aside from a short (5cm?) length of "piggyback" handlebar, held on with two improvised clamps, all the parts were original to the bike.
All controls were on the L/H bar, with the rear shifter mounted (upside-down) on the piggyback handlebar bit. The front shifter was in its normal position.
What would usually be the rear brake lever was attached to the front V-brake (US-style) and the other lever (to the rear V) was mounted adjacently on the bar giving a lever position below and slightly inboard of the front brake. The two levers were close enough to operate with a single hand, but there was enough of the front brake lever exposed to use that by itself quite easily.
The rear brake appeared to be adjusted less tightly than the front (ie, requiring more cable pull), this I would imagine was to help "balance" the two when both levers are grabbed together.
Although tricky, I can't see that it would be awfully hard to get used to such an arrangement, and it has the added benefit of requiring very little in the way of custom or exotic parts.
Mat
