Riding a 10 on the Saturday before a Sunday 50 is doable, see G.Obree 1993, 18:27 for comp record on the Saturday afternoon, 1:39:01 for comp record and national championship on the Sunday morning. You'll have more recovery time, as the Bossard event has been moved to a morning start.
Chasing 10 times >>>>>
H50/8 on the 8th of May <<<<<