Snow chains for HymerB 544

I am going on a trip to /Switzerland and need to buy some snow chains. the tyre size is 215/75 r 16..found some by Konig at a reasonable price. its which to have. There is a16 mm and 12 mm. I have tried a piece of timber between the inner wall of the tyre and the suspension strut and with 16 mm it seems a little tight for room. Any advice please.