I think Will Robinson is safe and sound. Take a yard of this fabric - 54 x 36 and use a good scale and you will come up with darn close to 13 oz last test i did it weighed 12.6 oz per yard

so there is no need for the WARNING.

and PS..we have clark material in now...and it is 13 oz.

<<Actually we have an evil plot to take over the world by selling lighter weight material.. see it works like this. first you get everybody in kilts, then you corner the market on Guiness beer and scotch, then comes the tricky part which involves getting mickey mouse elected president with goofy as Sec of State, we get a strangle hold on Quebec and cut off eastern canada until their supply of keith Beer is gone......

I wish The WIZARD of BC would just pony up, pay the couple of bucks to get some material, do a test himself