I’ve been using around a 3:1 ratio of the very same malto/fructo mix as you to my whey protein. Used to buy For Goodness Shakes recovery when on offer at Amazon and that’s their ratio.
Like yourself I haven’t found any gold standard around carbs:protein but is entertaining finding out what works for me at least.
But how exactly do I really quantify if it’s working anyway with work etc getting in the way? Should I change the ratio on hard days for example?