I've just ordered the Toyota 86 Greddy & Rocket Bunny Enkai Version which includes these, also ordered two sets (in 2 packs) of just the wheel arches from HobbyLinkJapan.
I remember using something similar years ago.
The thing to take into consideration is that time must be taken to 'form' the wings/fenders to fit the body shape exactly before gluing into place, and of course cutting the right amout out of the wheel arch beforehand. Sorry if that sounds childish to mention it that way but there is no offence intended.