For anyone reading this in the 2025 and beyond, you can now get a low profile allen key/hex socket. They will allow you to get to the filler plug with a ratchet. I would suggest only using the ratchet when torquing or loosening filler plug.
Example Amazone product.
Be warned though, you need an 8mm for the filler plug, the set shipped to me had two 7mm. But the 5/16 that came with the kit fit the same.