If I were in your situation, I would most definitely take the minimalist approach to documenting the system. If the auditor feels "uncomfortable" about auditing a scarcely documented system, too bad for him/her. You mentioned being aware of the ISO APG papers. There used to be one there for auditing with minimum documentation. That APG paper has been withdrawn but I attach it here.You think an auditor would buy that or am I setting myself up for a brawl with the auditor? I mean it is all in my head, other than inspection records, calibration records and job notes.