I toured for about two years constantly having problems with my ulnar nerve and numb fingers. Adjusted (almost) everything on my bike from saddle height, stem length, gloves, double wrapped bars, new bars, bought a bike with a shorter top tube.. anything you can think of. Some of the things lessened the problem but none really cured it.
On a lark at the end of last summer I tilted the nose of my brooks up a bit and haven't had a wrist/numbness issue since. Plus it's ridiculously more comfortable.
Strange how 'such a little thing can make such a big difference' (® morrissey)