[JustOneMore20]

You can keep 3...just find somewhere for the one. Are there more than one LFS in your area? If so, call the others and see if they take fish you can't keep. Tell them the situation and that you don't want anything in return. Some people like to buy bigger angels, so there should be a store that takes them.
If you don't believe that they will keep them, tell them you want to watch them put it in a tank.
Tell your friend you will give him/her the angel if they will step up on their tank maintenance....a big angel is worth about $15-20 I think, so tell him what a deal he's getting. Tell him the plec gets too large and he should remove it, start cleaning better, and you'll give him the angel.