Hi mate, Iv'e just put spacers (all be it only 15 mm ones) on my rears, also with OE 17's (my winter wheels/tyres), and I struggled to torque them down, so I went down the road with my wife following me.
I knew something was wrong at once, so turned around came back and she said it looked like a clown car from the back, with the wheels wobbling all over the place, so took them off and after quite a lot of investigating I found that the wheel hub bolts were patruding far enough to butt up against two casting points on the OE wheels.
Once I had used a large drill to remove these "bits" (it took a few fittings) the wheels now fit ok.
This may not effect yours because of the depth of the spacer is more (20/25 mm), I just thought I had better mention it, the pictures should show better what I mean.