LOL. It's not even going to come close to a 918 on the track. The 610 was already slower than a 570S in a straight line, let alone a 918, and 40kg is barely anything when you consider how heavy the car still is.

Would need to shed another 150-200kg


Straight line speed is only part of the equation. 

My GT4CS  gave up a lot to the 918 in that department but right now I am clocking in almost 10 seconds a lap faster than the 918. Granted I wasn't pushing the 918  very hard, but neither was I in the ClubSport and I was only on Michelin rains, not slicks. 

918 is the fastest among the trio of supercar only because it is a much better all around car, it will corner just as hard as the other 2 but it explodes out of corner quicker, the other 2 has a higher top end but that'a moot point as when cars reach that speed at the end of straights they have to slow down already, having spent the whole straight playing catch up to the 918.

Cornering speed is where the difference is.