They almost look too high, how they are sticking out significantly above the roll-bars. It can't be the headrests because they look like they are in the lowest position. Hopefully this is a matter of having the seat bottoms cranked up to highest setting and not a result of the 172 seats being substantially taller than the 171s.
I like the overall shape and look and the color contrast but not the oversized appearance on those pictures.
Good work, I hope the guy is very happy with them.
The R171 seats may not be to everyone's taste in terms of comfort (though I find them to be perfectly fine), but in terms of styling and elegance I think they are much better than the R172 seats. The cast magnesium section is very pleasing to look at and of course very light and strong.
The R172 seat are more chunky and more in keeping with the look and feel of the R172. I think the bolstering provides better lateral support than the R171 seats and they are comfortable.
On balance though, I prefer the seats as MB intended...