I've found the best thing for packing glasses is an old inner cardboard roll from carpets. They're thick, strong and round. You need plenty of packing top and bottom. A saw is the easiest way to cut them down to size.
I always double box. And put a layer or two of bubble wrap around the inner box.
Cling film is great for securing bubble wrap, much better than loads of sticky tape.
And I shake the parcel to make sure nothing can move inside.
I once saw porters playing rugby with the instruments belonging to an orchestra when I was flying. Since then, I have made parcels secure enough to withstand that.
Given this often means the parcel gets fairly big, a courier might be far more economical than RM.
"Star of Edinburgh" is one of Edinburgh's most prestigeous classic cuts. It is not one that gets outsourced. Good luck.
