On the weight thing, friend of mine has a hybrid 260Z with a RB30ET donk, my hybrid S130 two seater has a VG30DET in it. Similar specs otherwise eg both have half cages, and guess what? They both weigh the same, 1240kg.
Having previously built a hybrid S30 my preference is the S130. The body is stronger, aero is better and with a nose change and decent wheels it looks better, particularly around the side glass area where I think the S30 looks antique, compared with the rest of the car.
Quite simply I would never go back to a S30.