http://www.irs.gov/uac/Business-or-Hobby?-Answer-Has-Implications-for-Deductions
Among other stuff there is this tidbit:
"If an activity is not for profit, losses from that activity may not be used to offset other income. An activity produces a loss when related expenses exceed income. The limit on not-for-profit losses applies to individuals, partnerships, estates, trusts, and S corporations. It does not apply to corporations other than S corporations"
You need to talk to a tax person but I believe this means that you could offset any winnings with your comp expenses but not in excess of your winnings. You can not claim all of your comp expenses if this is not a business in which you have not been profitable in 3/5 years or have a reasonable expectation to be profitable.