205/40/16 are definatly the best size for an rsturbo imo run them for years with no problems at all, i have also been told by alot of people stretching 195,s on is dangerous.
you will need to get the proper wot they call (ghia bolts) they sell them at speedshack,they are the correct length and have the right size collar on for the job, using standard rsturbo alloy wheel bolts with a sierra wheel nut washer is also very dodgy, especially on the front,by the time you have put the washer on,its gone through the cozzy wheel then your brake disc and into the hub you have about 3 threads holding the wheel on! mmm nice! been there done that. dont recommend it get the proper bolts.