It not allowed in Elo, but you can if you are playing regular. You can have 8 of the same card as your deck if you want, but you don't get the bonus because it has to be 2 different for the same clan.
Ohno!! i never knew you can have doubles in ELO!!! awww! i just bought another pair, aww! shuckz! oh well...
Is it possible to play OLD with doubles?
Sure, the only thing you can't do with double is play elo.