DH Bike and tall rider?

Hey guys I'm looking into buying a downhill bike and I have been pretty interested in the Airborne Toxin as it is a good price (http://www.airbornebicycles.com/products/138-airborne-toxin-complete-bi…). I have been riding a hardtail thats a little too small for me for a while, and Im looking to upgrade. I would like to upgrade to a full suspension bike.The problem is I am 6'4'' but skinny and the bike only goes up to an 18'' frame. Ive seen other companies with downhill bikes with a little bigger of a frame but they are pretty expensive. I would use the bike for parks, but also some trail riding too, so Ill probably put a smaller chain ring on it to make climbing easier if needed. I am sure there are some modifications I can do to make it more "tall" friendly, but in your opinion do you think I would be too tall for a DH bike? If so, do you have any recommendations for me.