I understand your concern but what does your YSGCC do when he is up high. Is he terrified? Is he preening happily and taking in his surroundings? My GCC is flighted and sometimes flys in top of the curtain rod and I will immediately get her down because her body language tells me she isn’t happy. Does he step up happily when you retrieve him? And after you retrieve him how soon after does he fly back to the high spot? How long have you had him? I don’t think clipping is the answer but I wonder if he is flying high from fear. I would try bringing him out with a high valuation treat as an incentive to stay with you (fruit, nuts) if he flys up, retrieve him with the food but don’t put him away. Keep him with you and maybe try a tabletop perch or play stand on a counter or table (not on the ground or low) Keep an eye on the surroundings to make sure nothing is spooking him (loud tv, other animals, kids, etc.)