Did you notice what Rose wrote on p 482 TCB? Her base formula, in each case, has 1 cup/100 grams cake flour (or flour/cocoa combined). She found this was just right to serve 11 people (wedding, not dessert sized pieces). In practice, this amounts to roughly the amount of batter needed for 1 x 6” x 2”. Hence, RF2 = 2x6” and so on, up the chart. Batter loss to the bowl/beaters accounts for some of the anomalies, when the math doesn’t quite work out. See Rose’s note p 491. It’s not a perfect system, but it works! I can understand why you’d like to adapt it for your business.
I’ve been able to use this information to convert some of her other recipes to the Rose factor system. But I also pay very close attention to Rose’s “Understanding” notes that often accompany her recipes in TCB. She explains, on the basis of many test bakes - the empirical research Matthew refers to - why this or that ingredient had to be adjusted and in what way from the original recipe from which it’s derived.
From time to time in the blog, she mentions other guidelines that she also follows, e.g. a tsp of baking powder per egg (or 2 egg yolks) in most chocolate cakes…but not all. There’s that empirical research thing again! It’s why her cakes and her recipes are so reliable. Too bad other cookbook authors and commercial bakers aren’t as meticulous!
Bottom line, there’s no substitute for trying and tasting. Then tweaking. That said, if you’re modifying one of Rose’s recipes that’s already been tested, tried and true in the 9” x 2” pan, there’s some new, relatively easy math to scale up and down. Annie posted conversion factors late last year that she worked out for 2” high cakes of different sizes. Do a search for hers and Caspar’s posts, if you’re interested. Then, of course, you might need to adjust the baking powder depending on cake size.
To modify your pastry school recipes, what about using bakers’ percentage to scale them down to 100 grams flour (or flour plus cocoa or the like)? Use that adjusted formula as your base and then try applying the RF system? This is assuming you’re happy with the recipes as written in terms of taste, texture, etc.