You can just pitch the Rev Tent and set it in the bed / tub and the Rev Tent works just fine.   If it's going to be super windy and/or you experience heavy rains, consider using the guylines to tighten the tension on the rain fly fabric.    You can secure the guylines to just about anything.  We've used the track mounting points around the bed.  The trailer hitch, the rear control rods behind the tires, etc.   Just loop the line around the securing point and knot it and you're good to go!