Chess.com has already "fine-tuned" AIs that play at the N-elo level. E.g. 1800 elo, 2200 elo, IM, GM. I'm sure you could constrain stockfish to play at N+1 of y

Chess.com has already "fine-tuned" AIs that play at the N-elo level. E.g. 1800 elo, 2200 elo, IM, GM. I'm sure you could constrain stockfish to play at N+1 of your target opponent and thus avoid this issue.