That's a good question, Goat. First of all I would not take a recipe so heavily dependant on herbs and spices and immediately attempt to go twenty five times over. A better figure is five times over and reduce the seasonings by ten to tweny per cent. (You can always add more!)
Make up a batch and let it rest in the fridge for about four hours and then fry up a pattie. You can adjust seasonings from there. Another factor is that over a bit of storage time some spices and herbs actually increase their influence over the total recipe. In short, they become stronger.
Once you have comfortably established a five fold increase in weight you can then go five times again and bring a one pound recipe to twenty five pounds. Bear in mind that if you take a recipe that works with one set of ingredients you cannot always expect to achieve the same result by simply multiplying all the ingredients by the same factor. This is where the fun of experimenting with cooking comes into play! Ya just gotta keep doin' it till it is right!
Also, another little tip. Fresh herbs are anywhere from two to four times as potent as the dried ground type and tend to have a greater ability to increase their influence in the recipe during storage. I like to snip my own for dishes that I will serve immediately and fresh and depend on my usual brands of dried for my sausage and jerky. Keeps it predictable. (Somewhat)
Hope this helps you out a bit!