I wrote this 5 years ago if it adds any insight to the conversation.
Glycogen Supercompensation (AKA Carb Loading)
I'm an advocate of using liquid sources because it lessens the bulk of carb loading. Although I've reduced the total content from liquids from 5 years ago. I used to do 50/50, but these days I'm more like 60/40 or 75/25 (slanted towards real foods). I prefer to use Maurten 320 because it's absorbable using less water than traditional carb sources.
The above review does include a 2011 paper that uses data from recreational runners ranging from marathon times of 2:48-7:40 and and average of 4:33 (which is close to the US average marathon time). It concluded that ~7g/kg bw or higher of carb consumption was the threshold for seeing less of a fade when comparing pair-wise matched runners that did not consume >7g/kg bw carbs. It's not perfectly designed from what I remember, but it is good.
When I carb load I aim for ~12 grams carbs per kilogram body weight (or for me is ~983 grams carbs).
ETA - It is something you'd want to practice weeks before the event though and not something I'd recommend trying given the race is this weekend.