I'm a meteorologist and once chased tornados. I can say this with complete confidence, if your in the tornados path it will make no difference. Tornados will pick up fully loaded semis (that's 72K lbs or more) and toss them. You don't want to be inside.
My advice, have a low spot ID'd on you property. You're safer lying on your belly in a ditch (covering your head) than in a coach or a trailer.
With straight winds and hail, I'd think the safest would be in your coach, levelers up and air bags deflated; make sure your wheels are straight. that reduces the air that can get under the coach. Same if a tornado is near, but not on top of you.
If you hear the roar, find a low spot...otherwise hold on. Good luck.