True, so I will apply Martin's technique as described in a previous post. We'll see what kind of boil-off that will give.
Just a bit of anecdotal info:
My last batch was a Dubbel where I used my new 12 qt. pot for the first time. I had been using an 8 qt. pot prior and hadn't really been able to "let her rip" for fear of major boil over. So I typically would get a nice simmer going and call it a day.
This last batch, being armed with an extra gallon of space, was really ripping along for about the entire 30 minute boil. I mean roaring, turning over and damn near exiting the pot. I overshot my OG due to the reduce amount of wort from boil off. I typically factored in 0.5 gal/HR in my 8 qt. pot and must have overshot that a bit.
I will be returning to a gentler boil on the next go round. I can't say that I notice any negatives from really letting it rip, as I had a brief ferm temp mismanagement on that batch that clouds my judgement, but I welcome not having to boil like crazy, if only to reduce the amount of preboil volume I need to hit my numbers.