Just weighed both full stock and half stock for Brno 21/22. Full stock 1lb 11oz, half stock 1lb 14 oz. 
I'm sure it depends on wood, thickness, etc. from one rifle to another and from make to make. In my case, weight is not the reason to not use full stock.

I'm sure it depends on wood, thickness, etc. from one rifle to another and from make to make. In my case, weight is not the reason to not use full stock.