On the beer gutter, it says to make it 4″. That is with 2x4s and 2x6s; shouldn’t you leave room for a nicer finish, like veneer or some other wood besides the 2x4s and 2x6s?
Probak is absolutely correct – but you could also upgrade to the straight kegger bar which is a nicer design and slightly more advanced. Plus you get some workspace counter top area.