Rehoming A Plec - Yay Or Nay?

Hi all, as title suggests I have been asked to help rehome a plec for a neighbour of a friend. He cannot identify the species but says it is 3-4 inches long so not a monster but it is in rather a small tank compared to mine... The fear I have is it exploding in size and wreaking havoc with my own bristlenose plec and tearing up my plants!

Advice sought, please let me know your thoughts 

Anyone in the Scottish Central Belt wants a plec let me know 

I asked him to pose that Q to his neighbour... I'm reluctant to take it and feel guilty cos initially I said I'd take it but stupid me forgot to ask what size tank it was in. It might not be growing anymore where it is but putting it in my tank might trigger a growth spurt!

Does the neighbour think that the plec is fully grown? I was reading recently that this thing about fish growing to the size or tank available thing is a complete myth...

Well next step probably still to ID it to confirm it isn't going to be a small whale in a couple of years...