Infant Swing Set

Does anyone know if a swing hammock or just an overstuffed chair swing can be attached to rock a baby together? My son loves to swing, but it has a very dificil time with a regular swing because of some motor delays. He needs something to support his back and he is already too big for an infant swing. Is this possible and is it safe? Thank you-

Check out these links and see, it is useful

http://www.gardenfun.com/jardin-hammock- ...

http://www.hammock-superstore.com/catalo ...