Spent most of the weekend a week ago removing and hacking and grinding to lower the seat as much as physically possible. Checked the mechanism height before and after (while it was out of the car) and double checked again once refitted in the car - i gained an extra...
...wait for it...
Barely noticeable difference to be honest.
Will do a 'how-to-bugger-with-your-seat' thread with pics when i bring the pics and notes into work from home.
You will not be able to lower this particular seat type (Ti leather sports seats with red stitching) any more than approx 5mm lower than standard, at most, due to the way the mechanism is designed as it fouls on itself when you go below the standard lowest position. Increasing the mechanism movement also becomes a case of diminishing returns as well as the height changes less and less per amount of ratchet movement when you get that low.
I had to grind off mech teeth, drill and grind out end stops further and dig into the leather edging strip (leather is sewn onto a plastic strip) more than the seat does on its own anyway at the lowest height, then file a small part of the seat internal frame under the leather. Just for 5mm, probably wouldn't have bothered if i'd known the end result in advance lol.
You also wouldn't be able to remove any more than 1mm off the (approx 8mm tall) 'spacers' welded onto the ends (underside) of the rail mounts as one of the 4 is actually a large metal bracket (a few inches long) with a locating spike, it only has a 1mm raised bump to match the height of the other 3 'spacers'. If you found a way to grind/lower the entire bracket in some way, then any more than a couple of mm drop and the sliding rails would catch on the carpet edges around the mount holes anyway (that's what the spacers are there for, to keep the moving rails away from the edge of the carpet). Also if you ground these down somehow the bolt holding down the bracket corner attaches from the rear rather than the top, so you would also have to make a cut-out on the rear of the bracket to allow the bolt to access the threaded hole mount.
The only way to lower any serious amount would be to cut and weld the floorpan/chassis box sections to a lower height. The shaped floor carpet would also be screwed afterwards as it wouldn't be a fit any longer.
You getting the idea here? PITA.
Still VERY un-impressed with Alfa designers.
It may be that other seats (leather, momo leather, alfatex, non-electric recline, etc) are slightly different, but i'd imagine they all use the same rail and mechanism structure and of course they are all on the same chassis. Although the pre-facelift chassis's could possibly be slightly different, i don't know.