SFP planning: estimating total caseload

I am in the process of planning a response t(SFP) o treat moderate acute malnutrition that should run for 6 months. While I have the MAM point prevalence rate to work with initially (plus the estimated under-five population), I was wondering if there is methods out there to use in estimating how many beneficiaries might be treated over the entire 6 months. Questions going through my mind are should I be applying an incidence rate (and the recovery rate of course, from other SFPs in this context) and how does one derive this incidence rate? It would be great to hear how others are doing this. Thanks