Safty is an issue even with the space frame chassie, when somthing could break through the plastic, surpass past the tubes into the passanger compartment ( fence post, road sign or anything like that ), not to mention, in a rollover the plastic would break and turn into schards. Comparing apples to oranges is not the way to go ither, a Lotus is compleatly diffrent in relation 2 a Mustang, gearing is diffrent and the powerband is way diffrent between the 2, it's not all about the weight.