I believe the baseline is your estimated “maximum” capacity for carbs in your glycogen stores. You won’t be needing/wanting to be shooting that high every backload, unless you’re one of those extreme cases of “hardgainers”.
I vary my intake depending on training/activity level for the day. Right now, my training volume for each session is somewhat moderately high, so I do the following:
Upper Body – 1.5 g of carbs per lbs of BW
Lower Body – Up to 2 g of carbs per lbs of BW
I’m very sensitive to carbs (in an undesirable way) so any higher than x2 BW for carbs, I instantaneously get super soft and put on weight fast, but 1.5~2g seems to be the sweet spot.
Training Log: https://docs.google.com/spreadsheets/d/1vuwHRdBaPVILxxLhXly_N1Ys66Hcwk4j-bM7nvKSLrI/edit?usp=sharing