I would stack at the venue and remember, under each cake you need a cake board with dowels under it so it can support each cake. It will probably need a center dowel or two to be sure the cakes stay in place. Post a photo!
1 cup of shortening weighs 6.50 ounces. I always weigh it out rather than measure, much easier so if you take 16 ounces divided by 6.5 a pound of shortening equals 2.46 cups. like I said, much easier to weigh it out and not as messy as trying to put it in a cup and then get it out.
I too am interested in seeing if anyone can give an answer to this. I recently tried the regular icing recipe and loved it! All of my customers tried it on various goodies the last 2 weeks and they have said it is terrific. A neighbor said it tasted like an icing that an old bakery in her home town used to make. She said it brought back great childhood memories. I hope someone can answer this for us.
Just because you weighed something does not mean that a cup actually weighs 8 ounces due to the density of items. If you would like to cut everything down then figure out what half would be as far as weight and ounces of water. Don't forget the oil too, not sure how much it weighs. If you go to King Arthur Flour's site there is a weight chart that shows how much things weigh, like a cup of shortening only weighs 6.5 ounces ( think that it what it is). A very helpful...
Welcome Nikki, so glad you found this site and soon you will learn there is a wealth of knowledge here. Any questions or findings of your own don't be afraid to ask or share. We all have questions and thankfully there is usually someone on the site that can answer it for you and if not an exact answer, then you may be directed where to find what you are looking for.
I'm not sure what may have happened as I made many cakes from the 50 pound bag and all turned out fine. Not doubting that you follow directions well and all I can say is did you weigh your ingredients? I even weigh my water when I use the large mix. The cups are not standardized in the US and it is better to weigh it also. Try again and I hope all works out for you.