I think it depends on how many eggs are in the recipe. Or if you are using one of the gums, like xantham or guar guar to stabilize the cake.
The more protein in the cake and/or stabilizer you use the sturdier the cake will be and it will be able to hold more syrup.
I wish I could give you better advise, but like all gluten free baking there is a lot of trial and error involved. I always practice my GF recipes before I serve them to other people. And if I like the results, then I make sure to use the same name brands because flour blends can be radically different based on manufacturer.
If you can't practice ahead of time, maybe just add the syrup in stages to see how much you can add?
Good luck, and I hope you have a great Thanksgiving.