I think you're spot on. I'll struggle to fun fluently in my trail shoes on hard ground for 7-8 miles and I at least have some history of running slippy conditions on road shoes. Little steps and advance sighting should cover it.
As an aside, i've yet to find a good trail/road compromise shoe.
Both years I have run it thankfully the weather been kind and the ground on the trails has been firm enough to get away with standard road shoes. I'm wondering if this year it's worth breaking out the trail shoes?