winter wheels, retraction and clearance, online calculator?

[Mako]

so I found this calculator online

http://www.1010tires.com/Tools/Wheel-Offset-Calculator#

I was trying to see how my 335i winter wheels (from F30) would fit on my M3 (really like the wheels and would prefer not buying new ones).

they are 18X8.5 (square setup) ET35, used OEM lugs no centering ring required...

So BMW recommends 18X8.5 ET27 Front and 18X9 ET29 rear winter setup.
using that website to compare what I have to BMWs recommendation this is what it tells me:

Front = 8mm less clearance than BMW recommended size, also 8mm retraction into car.
Rear = SAME clearance as BMW recommended size, 12mm retraction into car.

So my biggest concern is front brake clearance! is that cutting it too close (standard brakes)? I would rather not buy spacers but also realize even if the brakes have enough space, the wheels will be retracted into the car by a decent amount.

I have discount tire do the season swaps for me (for free since I buy my tires from them), I guess worst case I go there and they tell me it won't clear the brakes or it does and it just looks funny and I have to go back with spacers... Just wanted to see if anyone here had input to my situation.