I have 17's on my RT ph3, and the front is dropped 35mm rear is pretty low, id say about 50mm because its in the arches!!
But handling is better than the standard wheels with my alloys on, and lowering it makes it handle better too obviously, massive difference!!!
But it sometimes scrubs on bumps at the rear, over bumps and that, and when i have stuff in the back (like big bags) didnt do this before i lowered it, not had any people in the back as i dont want to risk it!!!!
On the front only one of my wheels rubs which is weird, but i sorted it with my hammer and tennis ball, so no trouble really!!!
Hard braking sometimes scuff but thats because i have a 45 profile tire, will be going for a stupidly low profile, as low as pos when i need some tires!!!
I am going to raise mine at the back as its too low, and i cant use it for my journeys, but i reacon if you lowered around 35mm - 30mm on the back then you'd be laughing!!
Plus as its only a 1.4 you wont notice much of a speed difference, a bit on pick up and about 5mph id say on top end!!!
But IMO 17's look really good!!
Cheers,
Dumpy