Re: Filling the arches - 156
having seen the pics, I'd say they stick out too far, a little too aftermarket.
I'm not sue the black alloys help much either.
I have 17's (gen alfa, 3 sets) on my 156, on koi sports too.
The wheels don't look huge at all, just look about right.
All sets are silver.
not put the Ti alloys on yet but the 17" multispokes (147 gta type) look fine, the 17" 147 selespeed alloys, although no bigger actually appear bigger visually on the car, different design, more silvermetal on show?
I imigine the 17" Ti alloys will visually appear the smallest of the lot, perhaps because they have less alloy to see?
(my XJR has only 17" alloys, but they look huge on the car, again there is loads of silver alloy on show, its the 94-97 xjr)
Personally I think if your wheels were silver they would stand out more, thats just my opinion and personally taste though, non-the-less, your cars looks good anyway.