Baby should be rear facing for as long as possible as it's much safer, ideally until they are 12 kgs which can be depending on the bub well after 12 months of age (my 20 month old isn't 12 kgs yet)!
Laughing - my son was 13kgs at 1, and my daughter has just turned 3 and weighs 11kg!!!! She will be glad for her fathers slim build in another 10 years.

I have a SnS reversible bought for DS - DD still in it forward facing of course - I am going to hire a capsule for this little one hoping when he grows out of it my DD will be big enough for DS seat with harness .... wishful thinking I think at this stage, but I don't wanna buy another car seat ...