There isn't much for organized catamaran distance racing. There are a few keel boat distance races that have a few token cat's to guide the way. We just raced at Leech Lake in Minnesota about two weeks ago. The lake is 112,000 acres, the cats races a slightly longer course, about 30 miles. We always wound up back in the same place each day, easy logistics. The RC set about 11 marks and recorded the coordinates and set a course each day according to conditions. It was a good change from Windward leeward racing.
Another week long option is LOWISA (lake of the wood international sailing association) This is a fantastic week long event in northern MN southern Canada border. Cat sailors must charter a houseboat to sleep on overnight. But again the distances are in the 15 to 25 mile range.
Rainy Lake MN has another that sounds like more of a party then a race. Maybe I should look into that for next year, hmm.