I can't say for sure but I never had any problem moving up to 7+" fish. Most of the ones I moved of the larger size were 5-6" and I saw no problems at all. Caught later after moving them and caught one tonight that was 7.5" that was likely one of the 4-5" ones last year. I'm speculating here. No facts.
I personally would not want to move the 8"+ fish for several reasons. One would be the question you raise. The other would be that if the fish is already several years old it might not have that many spawning years left.
To me the ideal size of adult fish to move would be the 5-6" fish, as long as the LMB in the pond were not over about 15".
My only experience is with a pond full of GSF. By moving adult BG along with several hundred smaller fish, I now have up to 8" BG that I have caught (I don't fish this pond a lot so may be bigger) but even more important, if I put in traps I am getting a mix of GSF and BG fingerlings instead of 100% GSF.
I don't have a concrete answer for your question. It is just what I would do if it were me.
