Dukkillr,
You answered your own question. You made the change when you were young. An older shooter will have a much harder time making the switch. I've tried shooting portside and it was a laughable failure. It was only laughable because I didn't have to make the change. Had I needed to make the change, it would have been disheartening and frustrating. I had a friend who lost the vision in his lt eye and had to switch to rt side and it took him from a high (96%) lefthander to an 80% righthander. He was in his late 70's and couldn't even get his rt hand to pull the trigger all the time. I was proud of his persistance but saddened by his frustration. When he lost the vision in his rt eye he finally gave up trapshooting and said "well at least now I don't have to look like a fool shooting from the WRONG side".