Wheel Spacers to achieve flush with stock rims
 

I just acquired a great 2003 Lexus GS300 with stock alloy wheels. I am looking to add wheel spacers to front and back to add to stability and give it the more attractive flush mount. I have looked and it appears that I have to go to a 25mm in order to mount them without having to trim existing lugs or buy and install with new lugs. It appears that 25mm or even 32mm are good for the back wheels but I can find a definitive site to let me know what is the maximum I can use on front without having to do other modifications in the wheel well. Does anyone know how wide is the maximum on front and back? Has anyone done this to their GS. My last 99ES300 had hub centric spacers on it, and it made the car look and drive better. Advise?