The use of regular steel for the chassis of both your entries makes sense - it’s meant to save costs.
As for disguising the usually angular rear of the Stradale body sets, I adjusted the rear corner morphing zones to make them more rounded, and placed a body molding fixture on the upper edge of the rear end in 3D fixture mode to make it resemble a lip spoiler - the same trick I used for the LVC LS60, except that the LS40 I entered in PAIN has two circular taillight lenses instead of just one.