to each their own. but IMO welds need to be 15"
16s fit a mustang nice, some 17s look good, like the SVT rims are the only only 17s i like on a mustang
anything bigger than that fits better on a bumping caddy with hydralics or slammed on their nuts trucks. not a mustang.
and 15 inch tires are much cheaper than a 17 inch low profile tire, which u will definatly need with a 17 inch to keep from really affecting your highway rpms/gear ratio