I have a Venicci Gusto pram (www.venicci.co.uk/product/gusto-black/) which has the car seat, carrycot and seat unit.
LG is 15 weeks and fast outgrowing the carrycot - probably only got a maximum of 1.5 inches before she will have to lie with her legs bent. She is very long and growing lengthways very fast so I imagine I have 4 weeks left, maximum.
The carrycot does have a board that you can lift to prop them up slightly but, with no harness, she slips down as soon as you go up a curb.
The seat unit states not to use until they can sit unaided, but I'm not sure what my other options are tbh! You can tilt the seat back a bit and it does come with a harness.
LG is very good at head control but cannot sit unaided yet.
Does anyone else use the seat unit on their pram (any model) with success?