I'm trying to run solo via the http://solo.ckpool.org/ but however just a tiny fraction of shares are accepted. Is it possible to increase prevetively the minimum difficultiy form my (miner) side? I see the +diff option was named above. However I can't fid any relevant information regarding this option. How can  I use it with my USER(i.e. BTC address) parameter?

I'm using bfgminer, if it have a sense to mention.

Thank you!