I'm getting ready to do a test boil with my new keggle. Up until now, I haven't had the capacity to do 10 gal batches. On average, when you are doing a 10 gallon batch, what volume do you start out with in the BK? For those of you using keggles, how much do you expect to lose to evaporation during a 60 min boil? 90 min boil?