I feed similar Alex any protein done by Monday morning if not Sunday . Instead of dupurative I just put half gerry half barley . I don’t let the birds out to Tuesday evening anyway as I know they wouldn’t want to do to much ,it’s Tuesday when I swop to full gerry they may fly 30 mins at times on a Tuesday night other times close to a hour ( first loft fly of the week) but I don’t worry either way as by Thursday night they are doing a shift . My old birds only go out of the loft for 75 mins 3 days a week . I started the system to fit in with my work but I wouldn’t change it now
like you if I had them out Sunday Monday on this diet I doubt they would do 20 mins