Do I need to buy the very expensive 'baby set' if I get a tripp trapp for my 9 month old? We're trying to keep the cost down (DH insists on this chair and this one only) and have been watching some chairs on ebay. However, Granny has just given us half the price of a new one, so we'll get one. I have a 5 point harness/ reins set that says it attaches to most high chairs. Any chance it will work with the tripp trapp?