It's legal so in theory it's fine, a 6 year age gap isn't bad in the grand scheme of things BUT with a 16 year old and 22 year old you're going to be at extremely different stages of your life. The gap will be a lot more noticeable between a person doing GCSEs/A levels and someone who is finished or finishing university.
Whereas someone 23 and someone 29 would probably work better. Always depends on your maturity, etc. But someone 22 probably moved out with a full time job etc and someone living with Mummy and Daddy still at school? It wouldn't be my cup of tea.