Sorry to say but I dont think that really helps, perhaps need to clarify some of your comments and numbers to make things a little clearer.
There is no need to focus on the diameter of the rim (15" according to what you wrote) but rather
1. The total diameter of the tyre mounted on the wheel - with a 195/60/15 this is probably around 24.2" in diameter (note not all tyres are identical in measurements despite using the same basic sizings).
2. The width of the tyre (in this case a 195)
3. The width and offset of the rim (or backspacing).
These three factors will determine where the wheel and tyre sit relative to the wheel well and the wall of the well. There are plenty of people who have run wide rims by playing with the tyre width, total diameter and offset.
I am not that familiar with the vert so will refer to the GT/GTi
for example a 13x7inch rim with +40 offset will probably comfortably work on a GTi with a 205/60/13 tyre while same tyre, rim width but offset of +10 will stick out further (by 30mm) and foul on the fender wall. This tyre package has around total diameter of 22.4", very similar to a 195/50/15 tyre and not that much larger than the standard 175/60/14 (at 22.3")- ie. minimal effect on speedo and wont affect other things like ride height etc.
As you can see from this your tyre has a much larger diameter (which will also affect the speedo reading by almost 9% assuming your standard tyre is a 175/60/14).
To better see the impact of the tyre sizing and rim offset I suggest you have a play around with the following calculators
http://www.miata.net/garage/tirecalc.htmlhttp://www.1010tires.com/WheelOffsetCalculator.asphttp://www.autolounge.net/calculators/tirespacing.htmlhope that's useful and makes sense.