Hi Kelly - exciting news!

Maybe Tilly was an extreme case but I would never have got her to stay in one of those carriers as a pup - had terrible trouble carrying her even at nine weeks and ended up putting collar and lead on her to give me something to hang on to and keeping a very very firm grip indeed. She was very muscular, very wriggly and just wanted to be on the ground - and those kangaroo back legs were very very strong indeed!
I did post about it at the time on the Champdogs forum 'socialising wriggly puppy' and had lots of good advice but don't know how to link to it from here ...
Maybe your pup will be easier though (or maybe some of the carriers have some kind of harness inside?)...