most people on the P30 mailing list, the PO, and everybody we've talked to at the club, incl. our sponsor, says "You don't need it."
The Loos gauge is the first thing you should do. I will guarantee you that the people who are telling you that you don't need it are NOT experienced in rig tuning, and I don't care how long they have been sailing, they do not know what they are talking about.
If the things were not worth several times their cost in added performance and enhanced rig durability people would not have been buying them for the last several decades.