I have the same kit so I can answer from my perspective. The latest version of the kit is designed to use the windshield from a 2000 Infiniti i30. The curvature and dimensions are the same as oem, other than it is about 6" shorter at the bottom of the glass. This part is blackened out on the Aventador, so it is easy enough to paint fiberglass below the windshield to match. This part is also largely obscured by the wipers anyway. It costs about $130 for the Infiniti windshield versus about $5k for the oem windshield. To me, the cost savings (and ease of access to replacement windshields) makes it easy to overlook the slight difference.
The kit is mostly accurate along the sides of the car, so I'm using oem Aventador side door glass. Used Aventador door glass is relatively inexpensive (about $200 per side). The other two pieces of glass on each side aren't as easy to deal with. The oem glass is expensive and may not fit properly as the overall length of the kit is slightly shorter. I'll likely look at cutting these pieces from an old windshield.
