Looks good! I previously had 18" OEM replicas from OEwheels on my old LS430 and never had any issues with them. I am going to buy another set for my new LS430 as soon as they get them back in stock. I wish I took them off my old LS430 before I sold the car.
No spacers needed. There is actually plenty of room between the caliper and wheel. Even thought about having the mounting surface milled down to bring the wheel into the well a little more.
Any input on whether or not that would compromise the integrity of the wheel strength wise.??
You can have the mounting face milled to take off a couple millimeters but not much more than that, I'd say 3mm tops. For my 20" wheels I had my rears done at the factory before they sent them to me, took off 2mm to make sure they'd clear the fender lip.
The wheels look great! Why do you want to bring the wheels into the well more? Are you having any kind of rubbing issues?
The offset is about 10mm less than the Lexus stock wheels. They fit fine now but you can tell by looking especially at the front that the wheel sticks out a little farther than the stock wheels. They do not rub or stick out beyond the well but I wouldn't mind them being moved in a little. If not it's ok it's not a big deal.