At 5'10" 170 you will fit perfect in the Medium Flirt. I'm sorry there aren't any shops in Colorado yet carrying Fluid, but shops have been slow to pick up new brands recently. Hopefully this will change soon. I will be out at FIBARK and Gunnison with demos that will have the all new outfitting. I'll also have the new Solo Creekboats. Drop me a line directly at email@example.com
if you have any other questions. Be sure to speak directly to your local shops about your intrest in the Fluid boats, this will help them in deciding to pick up Fluid.