I am wondering how you would like to palpate the tendon since it is partly covered by the acromion so impossible to palpate. another problem might well be the possibility you are palpating other structures like M. Deltoideus, Bursae etc. (for shure in the more muscular or bigger person)
I personally would stick to an X-ray or do you have any objections against the use of X-ray as a diagnosing device?