I would have said that C4 is already a decent supp in its own right. You shouldn't need to supplement a supplement. If it's not working and you're only having it for the taste, then you're having it for the wrong reasons. It's a preworkout, it should be shot/skulled not sipped on.
You can have more Creatine but an extra 5g of mono is hardly worthwhile IMO. I'd be having more like another 10-15 at least. 15-20g of mono over the course of the day seems like a good amount for most, maybe 10% of that if it was all nitrate as they say it's easily absorbed... No idea if that's true but one things for sure, it would be exy as fark to run the same grams of nitrate as mono.