a 205 50 15" tyre is going to be shorter than a standard 205/45 16" so i can't see why there would be any problems, using the correct offset and width of rim of course.
So they are the same width and the height from the hub is shorter, providing the wheels they are fitted to are the same offset and width, they will clear absolutely fine.
Height isn't the issue, r888 tend to be wider than they quote 195 is more like a 205 road tyre.
The problem is that the inside of the tyre is likely to rub due to it being wider and that I want more camber on the front that will bring it even closer. (i'd say there's circa 10mm between tyre and damper body on standard wheel and tyre.)