5 gallon vs. 6.5 gallon fermenter

[TheImmaculateBrew]

In jamil's brewing classic styles book, he recommends creating 6 gallons of wort to end up with 5 gallons of finished beer.
Are his recipes made specifically for the larger batch size? Or can I take any recipe I find and put 6 gallons in the fermenter instead of 5? And if not, can I just scale up each ingredient by 6g/5g = 1.2 to adjust?
Because I would like to end up with 5 gallons in the end.

 

[Arkador]

just multiply your ingrediants by 1.2
I make 5g batches, and usually end up with a nearly full keg. If i make a 6gal batch, I always have extra to bottle.

 

[yodalegomaster]

Why they use a 6.0 gallon batch is there is "always some loss" when you brew a batch. I loose about 3/4 of a gallon to trub and hot break removal in my boil kettle. They want you to hit the gravity's with this loss in mind. If your brewing stove top / extract you might not have the brewing losses, and think you need the 6 gallon fermentor. I would still use the 5 gallon fermentor and just add enough water to make 5 gallons. You can alwasys add distilled water if you need to at bottling.