[ZHPizza]

Adding some info to this thread as I continue to search for ways to make these manual sport seats go a little lower.
It won't let me insert the pictures in line, so I'm just going to have to describe my findings here in a big block sorry guys.

So I pulled the seats out to see if there was any room to gain. Found nothing on the seat frame itself (no surprise), so I started looking at the mounts on the floor.

So looking at where the seat sliders mount, the rear sits right on the rail. Nothing to be done there without cutting and rewelding the frame.

The front, however, sits up on a boss that is 18mm higher than the rail. I got to looking at it and saw that it continued down through the rail, so I took some rough measurements and found that there was about 26mm of threading all the way through.

I wanted to see how it mounted so I got out the borescope and took some pictures from inside the rail. Looks like it anchors hard into the lowest section.

So could we cut that boss down and reduce the height of the seat? Sure! Would it be safe? Let's see...

The rear mount has a thread depth of 10mm, which holds to the commonly accepted thread engagement minimum depth being equal to the diameter of the M10 bolt.

The front mount has 26mm of threading, so you could theoretically cut 16mm off the top of that boss and still have the 10mm to meet the rule. Hell you'd probably be fine if you cut the whole 18mm exposed portion off as you'd still have 8mm of threading anchored under the rail.

Is it worth it? That depends on how much space you're after.

I was going to lay out some triangles and do some math, but then realized I could just do a practical experiment. I set the seat on a flat surface, then added 18mm blocks under the front mounts and measured to a point roughly where your butt would be (call it 2/3 of the way to the backrest). Then I pulled the blocks and checked the difference: 10mm

So if you cut 18mm off of those front mounting bosses, you'd likely see 10mm of increased headroom. Is that enough for you to be comfortable?

Edit: added a crude drawing of what I'm seeing