Anyone tried the new Mountain Buggy parent-facing carrycots?

[Phalarope]

We've got the old version MB Swift, which we bought because it was small. Brill for 2nd centile DD...but DS is helpfully on the 90-something centile for length and is already looking rather squashed in the carrycot at not quite 3 months. Don't want to turn him round and lie him flat in the buggy so soon*, so was considering buying one of the new carrycots, which convert into a parent-facing seat. They're supposed to be compatible with old models. Has anyone tried one? Are they a decent size in parent-facing mode?

Don't really want to buy another buggy as we've found the MB Swift works well for us otherwise.

*(this may be partly sentimental because he'll be our last, and I'm not ready to say goodbye to the baby stage just yet)