The Freeride, Street, and Slim saddle foam are trimmed as close as possible to the edge of the frame, so width is similar.
The thickness of foam at the bottom of the cutaway is similar (is minimal) for all models; the cutaway is deeper in the models with thicker foam.
The thickness of foam at the very front is similar between all models (as close as I can get it) - all become very thin at the front where you don’t want bulk. At the very back, the 2011 Street and Slim are the same thickness and the Freeride is very slightly thicker.
Here are foam thicknesses in the middle:
Freeride: 45 mm
Street: 25 mm
Slim: 15 mm
If the difference between the Slim and Street doesn’t sound like much in absolute terms, note that the Street has 1.7 times as thick foam as the Slim, and the Freeride has 3 times as thick foam as the Slim.
In terms of curvature, the Fusion, Street, and Slim have the least to most curvature, in that order, due to the change in foam thickness in the middle. However, in practice the difference is minimal because you sink into the Freeride foam more, and because the bottom of the cutaway is the same on all models. The Nimbus gel has the most curvature. Although I know there have been some comments against high curvature here, it’s worth noting that many riders do find higher curvature comfortable and good for control when turning. It really does come down to personal preference.
I completely agree that saddle angle has a huge effect on comfort - super important to experiment to get that right.
At the heart of the saddle is the frame. The current KH saddle frame is 10 mm wider than the old KH frame at the position of the sit bones (the old version being the one that’s still used on Impact and Koxx-One saddles). I find this noticeably more supportive than the old saddle, where my sit bones seemed to overhang the edges.
Lastly, for what it’s worth, here is what I use:
Fusion Slim: on my KH20, for trials
Fusion Street: on my KH36 for distance, and on my KH24 for technical DH.
Fusion Freeride: on my KH26 for All Mountain and XC riding. I also prefer the Freeride on my KH36 if I’m distance riding offroad.
Hopefully that info is useful. It’s a real challenge to come up with a range that fits the huge diversity of riders and riding styles in the sport, and that can reasonably be produced for our small market. However, the Nimbus Gel and the 3 Fusion saddles together make up a wide range of options and I think we’re starting to get closer to this goal.
Cheers,
Kris