74g of carbs per hour is plenty - and enough to cause GI distress if you haven't trained your gut. If you have enough time before the race, work on training your gut and experiment with different brands / carb sources.
Once you've figured out what works for you, stick to that. Don't experiment on race day. Don't under-fuel because you feel OK in the moment. Don't eat from aid station tables unless you run out of fuel. It's way too easy to see a bowl of Haribos and smash a handful with a litre of Pepsi, only to realise half an hour later that you've made a mistake (I say this from personal experience )
One thing that I would add is electrolytes. They'll definitely help to reduce chances of cramping. If your drink mix doesn't have them, then consider adding an electrolyte tab every hour. I'd also agree with having one bottle of drink mix and one of plain water. If you need to cool down, you really don't want to be spraying yourself with drink mix.
