My wheels are et35 and I had to put spacers in the front to get clearance on my big brake kit
I wouldn't advise you to put spacers on the rear just leave that be, on the front long stud and get some decent hub centric spacers eg: eilbach and that should give you the clearance you need
The other route as you know is to buy alloys with offset to give you clearance but that is the far costlier option
Luciano