It is very difficult to hold my 2 -With Tigris I would never try and with Filou I have to be extremely decided. Both of them don't accept to be petted when you hold them -they have to decide when to cuddle.

So going to the vets is always a drama. My carriers open at the top, which makes it easier: catch cat -drop cat in-cover closed.
They yowl all way to the vet (4 miles long I'm glad she's that close) but at the vets they behave unnaturally good. I am not sure why: it might be out of scare but also out of curiosity -being quiet as long as so many new informations go into that little brain.

So if you manage to catch Calvin it is not sure that he will play the full drama at the vet's. And most vets can deal with it.

Of course it may happen that he will not talk to you after such an experience (one day Filou fell in the bath tub -I caught him and dried him with a towel- he did not talk to me for one day -and he's not feral!) but I think he's on the confidence road and after some days he will be there again.

Good luck to the both of you