@Paul ******
if I understand the OP's post though, they are saying they wish to continue using the old passport (presumably for entry stamps) since it still has space, even though the DTV was issued for the new passport. This is what doesn't make sense, as the old passport should have become invalid as a travel document when the new one is issued, so can no longer be used as the entry passport. This is not the same as having a valid visa on the old passport, which can still be presented to enter on the new passport.