my dd is 6 1/2 months, she can't quite sit up unaided (couple of seconds at the most) we feed solids in her bouncy chair however she is always trying to sit up, went to MC to buy a highchair and was told not to get one till she can sit up unaided even tho all high chairs say "suitable from 6 months or when child can sit unaided" so don't know what to do, any suggestions?? should I go ahead and buy one, she should be ok if they have the safety harness things shouln't she??