I am not sure what special ability to give

[Sully]

DL/DML or DR/DMR?

I think Wall would be appropo, but I used to give Corner.
As they are usually outside defenders, I give Wall instead of Aerial, which is what I usually reserve for inside defenders.

Does this make sense?

[Steppenwolf]

If they are tall, don't give them wall... lawl

[Gert Funck]

for sale? high, then aerial if low then wall.

For keep, use on skill

[Staggy Stagg]

Never been a fan of wall SA, most good FK takers will beat a wall, generally go for other SA's myself.