What is the measure for scaling cinnamon if you double a recipe? I love bread and butter pudding. We came across a recipe, and had plenty of ingredients, so decided to double everything, including double the cinammon. 

This almost worked out perfectly, except that it suddenly felt like we had way too much cinnamon. It was almost as if we should have left the original quantity of cinnamon whilst we doubled everything else. 

It seems to me there must be some scaling factor for cinnamon when doubling up a recipe. Something like 2x the recipe but just 1.1x the cinnamon. 

My question is: What is the measure for scaling cinnamon if you double a recipe?
If you never prepared the recipe as written (which appears to be the case), you have no basis to tie the way it tastes when doubled to doubling it, rather than to the proportions of the original recipe. 

Based on many years of making many things in many sized batches, if I double a recipe and want it to taste the same as the original recipe, I double the cinnamon. 

I conclude that the most likely case here is that the original recipe had a lot of cinnamon, and that what you tasted is simply the way it tastes. 

Depending what travels the recipe might have had before you met it, there's also a not-uncommon error that occurs with US measurements sometimes - the confusing (by some transcriber in the past) of T and t in hyper-abbreviated notation, which can make a factor of 3 difference (T = Tbs =Tablespoon = 15 ml, t = tsp = teaspoon = 5 ml.) The copy of the recipe you are looking at need not be hyper-abbreviated for this to have happened to it at some point in its past