Changing a trim pot is not physically modding a unit but I would mark the original position. I can understand Tesoro or for that matter any company wanting you to stay out of their control box as untrained hands can cause damage and could cause warranty problems. Having said the above personally like Tesoro notch units and have set a few in my day to my spec's and some of the manuals tell you the notch is adjustable but better set by Tesoro tech's. Usually a talk with the powers to be will tell you where they are and how to adjust at least they have in years gone by.
As far as ground balance pots mineralization vaties greatly and sometimes may change several times in the length of a football field so know what you are doing lest you do more harm than good...Indeed Monte brings up some good points in his posts however unfortunately we all do not have his expertise so be careful even if its only a trim pot and physically mod a unit and for sure you are taking a chance of voiding a warranty.
As far as ground balance pots mineralization vaties greatly and sometimes may change several times in the length of a football field so know what you are doing lest you do more harm than good...Indeed Monte brings up some good points in his posts however unfortunately we all do not have his expertise so be careful even if its only a trim pot and physically mod a unit and for sure you are taking a chance of voiding a warranty.