Pull your FTL from the booking and not using OLCI will usually give you a chance of IDB/VDB on a full flight.

On weekend flights, many people wouldn't accept a VDB because most would want to get back in time for work on Monday.

Few Sundays ago on BCN-GVA flight was overbooked and I as SEN got an op-up, whereas a friend (no M&M status, no OLCI) who was on the same flight was waitlisted (and then given a seat by the C/I supervisor when they saw he was travelling with me).