Cuould you give us some pix? Reading your post again I am thinking this could be "just" a wrist problem. A lot of peopel riding bikes with flat bars have tthe same problem. Could be more about the angel on your wrists than distance from seat to bar. Do you use "Ergon type grips"- or do you know what it is? You can buy them with short barends or without. It is possible you can buy it locally to try out.
Thor sell some Biologic ones that are great but there is a lot of different ones.
http://www.sjscycles.co.uk/handlebar...c-dept899_pg1/