Here are (or where) the tourny rules http://www.spyder.tv/spydercup/section/rules.html
Quoted from the rules..
Spyder Markers Only
Every device used to propel a paintball during any Spyder Cup 2007 event must be a Spyder paintball marker and must be recognizable as such. Upgrades to the barrel, regulator, feed neck, grips, bolt, expansion chamber, and external cosmetics will be allowed as long as the marker can still be easily recognized as a Spyder marker and the basic functioning of the marker remains that of a Spyder. At no point may the Spyder name or logo on a marker be covered or removed. Each player will only be allowed to carry one marker with one attached barrel during each match.
So basically, make a "Sleeper", the best most competitive marker you can as long as it still looks like the manufacture had something to do with it. And you notice they don't mention an after-market board in the items that where allowed to be upgraded.