At what point is it best to switch to SV background mode?

[prmango43]

In a fully auto roast, if I choose to background align roast at DE to avoid potential temperature mismatch at Charge when switching from SV manual mode to SV background mode should the switch be made:

1 -- just before start, or
2 -- at Charge, or
3 -- just after Charge, or
4 -- close to TP??

TIA

Kaleido Dual M2S AS 4.0.2 Windows 10 Pro