Beer Dr,
When it comes to specs like that, I would remember this. Sure you are not talking about another instructor? When I discuss this section of the workshop, I note that you should build each line with the same restriction across the board. Guinness folks will tell you that they want a certain pressure at the faucet to acquire the cascading pour (I forgot what that is) and to adjust the pressure from 28 PSIG for direct draw up to 40 if required based on the length and restriction built into a long draw system.
Now who is to say that the Guinness is going to be dispensed from thaat line all the time. If it is removed, your are set up for an ale or lager.
Scott Zuhse, Instructor
Micro Matic Dispense Institute