Tony, I don't use promash so can i ask - utilisation is 5% greater compared to what? A sixty minute boil? A 20minute boil? I have seen quite a bit of conflicting opinion on the effect of FWH. I used it on my last brew (an english bitter), the recipe called for a 20 min addition of EKG and I threw it in as FWH instead. The beer has only been bottled for 2 weeks, I've tried oone and it had a lovely hop flavour without excessive bitterness, so FWH seems to work OK but I'm not sure of impact to IBU.I use a 5% increase for FWH'ing in Promash
Hers is how i set my hop utils
cheers
hazard