Anyone eating close to 5k in the offseason is probably going to be starting his diet at close to 500g, especially easy if cardio is increased concurrently.
I really like finding a "base" amount of carbs per meal, then doing 150% of this amount of first meal and post workout meal, and doing 50% of that amount for last 1 or 2 meals, depending on training time.
This is one of Chris Aceto's methods.
Amount of carbs while dieting... my answer to this question would have been much different 10 years ago...
What is your answer now and what was it 10 years ago if you don't mind me asking?
Looking back and comparing the amounts of food I used to eat during my best years in this sport (let's say from age 18 to 27... I'm now 34), I can only make the following observation: my metabolism has greatly slowed down over the years.
Where I could lean up easily with 300g carbs/day (while keeping fats at a reasonable level), I now need to halve that number if I wanna see substantial fat loss... cardio or not.