Speaking of low acreage trail systems, have there ever been any conversations with the city over their parkland off the south Walnut Creek trail? 200+ acres of park and utility easements, 100 ft. of elevation change, pre-built return trails from phase 1 and phase 3 of the SWCT, plus easy access from Gus Garcia Middle School might make after school programs a selling point when all the craziness is over. The city marked out the farm fields on the east side of the paved trail for a sports complex development next to the Austin Tennis Center. Everything else looks unplanned so far.
Considering other urban bike parks - Valmont in Boulder is on 40 acres, Duthie Hill in Issaquah is on 120, and Bentonville's Coler is on 400, it seems like there might be ample space for trail development.