Hello,
Oops, you're definitely right, I had forgotten to take into account the total and didn't notice that we were already over the 55mm ! :-(
I was used to standard OAG version and of course we don't need the tilt plate to connect to the telescope, therefore I had the usual elements in mind after the OAG and it was within the 55mm with it included...
So it's now crystal clear, I'll have to buy the 15mm adapter but alas, it'll be less comfortable to change my filter, but I've no other choice at the moment...
Thanks for your explanation.
Philippe