During the scene where Don is making a tandem skydive into the Selleck dealership, there are a number of obvious mistakes regarding the parachute gear: You can see there is no main parachute connected at the "three ring circus" connector point on the main harness as the two are in the aircraft doorway; There is no drogue parachute used during the freefall; Under canopy, there are only 5 or 6 straight cords connecting the parachute to the harness, instead of 10 to 12 split lines; The parachute the two land under is very small (less than 200 square feet), instead of the 400 - 500 square feet required for a tandem rig; and when Cessna Jim pulls his parachute up after landing, it is not connected anywhere to the harness.
As seen from the beginning, the Trans Am is placed on a metallic support in the air. By the end of the movie we see Don and Ivy talking inside the vehicle. However, when exiting, Don gets down as if the car was on the ground, before the take was quickly cut to a next scene.
While trying to convince "Paxton Harding" to purchase a vehicle, "Don Ready" suggests he take his band on a tour of the Florida Panhandle. The first city he mentions in Gainesville, which is located North Florida, not the Panhandle.