It's hard to figure what is what on that picture. But as Andy hinted at, "lower" doesn't mean lower when sitting on the wheels, it means lower when in straight and level flight. So, how are the tank and engine in relation to each other when the plane is "level" as it would be in flight? Wheels don't count .

Using the engine thrust line as "level", then the tank isn't really all that low, nothing that I haven't seen in plenty of planes. I'd say your best plan is to rotate the engine to a side-mounted or 45degree mounted arrangement if possible. Otherwise don't sweat it, to fly and see how it does.