the 2 oz. cups weren't used for the 19 cup bouquet, well they were but I'll explain!
The 19 cup bouquet is done using a 5 oz. cup, it's a normal plastic drinking cup so it's tall (maybe 3 to 4" from top to bottom) you staple those together.
I hot glue the 2 oz. cups inside of the 5 oz. cups when doing the large bouquets (because I'm paranoid that the cc's will fall down inside the tall cups and get ruined), because the 2 oz. cups are short (maybe 1-1/2" tall top to bottom).
I used ONLY the 2oz. cups for the pink cc bouquet in the printed flower pot, it contained 7 normal sized cc's. Those were just simply stapled together with no trouble, but 19 of them won't staple together because (as you found out) the angle is off because of the height of the 2 oz. cups.
Here is a picture of the 19 cc bouquet with ONLY the cups....granted the edges of the cups have been covered up with tissue paper, but you can get an idea of how tall the cups are. HTH sorry I didn't explain it better before. Oh and I get the 5 oz. clear drinking cups at wal-mart I think they're in a pack of like 50 for $1.99!