Super D (SD) is a blend of cross-country and downhill. Most of the race is downhill, on trails similar to the downhill segment of a cross-country race. There are also short (100–500m) uphill sections which make the use of downhill bicycles difficult, as a result, most riders use cross-country or ‘trail bikes’. Depending on the trail and race venue, the start may either be seeded (riders start in short intervals), or Le Mans mass start (riders run to their bikes, timing is started when the riders start running). Probably the most famous of this type is the Megavalanche.
I’m looking at building something up but based on more of a jump frame, maybe thinking a bit more grr is needed, perhaps a SURGE like the one above 😉