How many carbs/protein you'll need to consume will be determined solely by your level of insulin sensitivity. Variances in inulsin sensitivity can cause dramatic differences in how may grams of carbs/protein will be needed per IU, so this question cannot be answered without knowing this information. In general most people will need betwee 8-12 grams per IU.
In addition, BB'rs need to start moving away from the overly simplistic mind-set which asks how many "carbs" they need to consume in order to cover a certain amount of insulin, as this addresses only a singular aspect of insulin use....and they need to start asking how to maximize the muscle-building potential of insulin. Some of these relevant factors include protein/amino acis consumption, as well as macro nutrient ratios (fat not included).
When using insulin, protein/amino acid intake should be a priority, as they are the only macro responsible for directly initiating muscle growth. It is amazing to me how many BB'rs are focused so strongly on their carb intake when using insulin and how little thought they put into their protein/amino acid intake. This is even more baffling given the fact that almost all BB'rs underastand the importance of protein/aminos when it comes to muscle growth, yet when using the most potent nutrient shuttler in existence, this mentality goes completely out the window. Why?
When structuring one's nutrition around their insulin intake, the first thing which should be determined is total macro need. I say macro need and not carb need, as fast digesting protein will "use up" injected insulin as well as carbs. The 2nd determinant should be protein/amino acid requirments, as neglecting this vital aspect of nutrition while insulin is present will short-circuit one's potential for growth.. In fact, one should focus on the consumption of this macronutrient even more strongly during this time frame compared to the rest of the day, as the ability to capitolize on this macro's growth potential is enhanced during this period. Only after one's ideal protein/amino acid intake has been determined should carb intake be evaluated.
Certainly, carbs play a very important role in the growth process and their intake should not be neglected, but maximized. However, it makes no sense to perfect one's carb intake while neglecting protein/amino acid intake. Insulin should NEVER be utilized without protein/amino acids. I can think of no reason to neglect this vital growth component when nutrients are being shuttled into muscle tossue at an exagerated rate & degree, so when determing your carb requirments, make sure to focus on protein/amino acids requirments, as well.