My daughter's friend has requested one of those oversized Toblerone boxes and since I fly next week, I've promised to *attempt* this.

ARN-MUC-CLT

Can I buy this at ARN and expect to keep it during transfer at MUC? I'm pretty sure there will be another security check in there somewhere.
Better to buy this at MUC and if so, is there a store after security that sells these?

I have a little over an hour between flights, but if there is any delay leaving Stockholm or landing in Munich, that could really impact purchase time.

What should I know *before* I try this?

And finally - the CLT flight is pretty full and that box is pretty big. Any trouble taking that on board and stowing it in an overhead? My other carryon items will fit under the seat, no problem. My coat will stay on me as a blanket and I plan on resting for those 10 hours - but will I get grief for an item too large to take as a carryon?

Thanks for any insight!