It´s annoying that there´s no 20mm front and 135/12mm rear options for the wheels. Can´t be that hard to make some end cups for that. Same thing with SRAM´s rise wheels.

Yeah, you can buy them, but I don´t know any factory made spike tires that could win DH races(ofcourse possible, but not probable). There was one from Nokian, but they stopped producing it and the ones left are now worth of gold. I made my own spike tires few years ago to a nokian gazzaloddi G tire, but after two winter-dh race seasons, I decided to replace the side spikes with 15mm screws and left the spikes only to the center of the tire. I haven´t tested them yet, but I hope I get seconds off of my times. Downsides are that screws are heavier and you need to put protection between tire and tube makes them even heavier. Also the risk to get a flat is higher. EDIT: for the topic, I´d like to see more this kind of racing and to get to participate in something like this!