Tell him to go to the sport physio in North Freo. Balancing out the shoulder muscles to increase stability seems to be a better sustainable solution to taping.
I've killed my shoulders after almost two decades of competitive climbing and lots of surfing. Stability specific training was the best thing I did.
Shoulder instability can arise for a few reasons either previous trauma compromising the integrity of the joint, being too mobile, or poor control of the muscles that support the shoulder joint. Either way getting those issues while surfing can be annoying and a bit painful at least or dangerous at worst due to the inability to paddle back to safety if required.
I am a physio who has worked very closely with the Perth Shoulder Clinic (orthopaedic surgeons specialising in shoulder surgery) and I have my own clinic in Fremantle. I would be pretty happy to look at your friend and give him some options on how to move forward on this.