Speedbird, when i raced in the past (restarted last year) used to try all kinds of systems and had the field thing you describe for a long time, everything they need is in the loft but they used to circle the fields and sometimes drop, never sussed it, whether chasing hens or bored but eventually it seemed to right itself.
Regarding feed i did virtually the same as Jimmy White, even holding the widowhood mix back til Wednesday afternoon with good results. Nowadays, people are using Gerry plus and Diet and similar to Spelbin i'm trying it but in my case without any success.
Spelbin, not teaching my granny to suck eggs but i always found if they got too much of either depurative or mix all week they didnt show as well, liked to have them looking for something on Friday and the ones that ate well friday usually turned up.