CISI Fund Services: Valuation Exemptions & Cost Attribution

I am currently nodding off with my eyes closed trying to digest the valuation exemptions under the CISI Fund Services module. The concept of where the "custody" ends and the "administration" begins really reminds me of trying to pick a support level on a stock chart—too much volume and the support breaks, but too little and you get stopped out early. My biggest headache is distinguishing between a statutory exemption for an amount held in a joint account versus a mixed client money account. Is the exemption purely based on the physical segregation of the accounts, or does it hinge on the existence of an implicit banking contract between the parties involved? I just can't see how you categorize the funds when you have three different high-net-worth individuals pooled together but no explicit agreement to treat them as a single legal entity. Pricing and cost attribution is giving me a headache that looks worse than a margin call. I am stuck on the rules regarding the deduction of costs from client assets. In the market, you know exactly what your commission is per share, but with these funds, it feels like trying to calculate slippage on a volatile overnight swap. The fund administration guide outlines strict rules on when a cost must be borne by the fund, but I am struggling to apply the commercial reasonableness test. Does anyone know if the costs must be allocated on a pro-rata basis to the specific asset that triggered the cost at the time of purchase, or can we spread the operational overheads across the entire portfolio regardless of the transaction? It feels like I need a crystal ball to predict how the auditors will view the allocation of these flat-rate fees.