The idea that teams would do significantly more damage targetting a 5ft 5 fullback than they would would a 5ft 7 fullback seems strange to me. Either way, they're short and not winning many headers against anyone who wants to target them in that way. Luckily that's only a small part of a fullback's job, which is why you have so many short fullbacks.
In terms of of aerial duels Lamptey has been winning between 26-33% across the last three seasons. Whereas someone like Trent Alexander-Arnold has won between 22-45% over the same three years. If we take Lamptey's average (28.8%) and TAA's average (30.5%) and apply that to the average amount of aerial duels AWB has faced in his full seasons here, it would amount to the 5ft 9 TAA winning one extra aerial duel a season over the 5ft 5 Lamptey were they both playing for us.