Is it ok to bake a cake with the cake mix extender recipe today, and not serve it until saturday? I have never done a cake with the extender so early, but I won't have time tomorrow ... also, here is a dumb question, but is 8oz basically a half cup of sour cream? I only have a huge tub of sour cream and no scale to weigh out 8oz ... thanks for any help!

8 oz. would be one cup.
In my experience the cake will be fine Saturday. You didn't say if you would be decorating it. If you are just frosting it, you could freeze it until Friday night, let it thaw overnight and frost it on Saturday morning

thank you ... I will be decorating tomorrow, but a very very simple design! I will bake today and make the icing, frost and decorate tomorrow, and it will be ready for saturday! Thanks again!