A couple weeks ago, I tried to ride my 17h horse under 17h-ish fallen tree. For the non-horse world, I tried to ride 5'9" horse (at the shoulder) under a 5'10" fallen tree.
This is not what happened.
This is what DID happen.
"Crap, crap, crap, AW CRAP!" SPLAT! (did I mention that this was the squishiest section of mud on the ride?)
I mean, I did duck as low as possible over the horse's neck. But between the head and shoulders, there's only so much a T-Rex can do... There might have been some magical thinking at work.