The QC aircraft are very easy to re-roll either way. I watched one in BFS when the concept was new and a pax to cargo re-roll was completed in 11 minutes. The reverse took a little longer as, at that time, a bulkhead partition was put back in and this always took a few minutes longer to assemble than breakdown.
I've also watched the NCL operation, albeit a few years ago when Servisair were handling. Again, done in a few minutes.
GH