ORIGINAL: Dr Kiwi
I think you are bound for trouble - though the initial voltage may be the same the cells are different in terms of internal resistance and one pack will drop more voltage under load (so they will be mismatched), and one will drain before the other.
Sorry, but the electrochemistry will not permit this. The packs will discharge evenly in proportion to their stored capacity.
See
www.rcbatteryclinic.com - article on parallel operation for detail explanation.