Alright, so I made a big stink about it in another thread and said I'd do a write up. It's going to be more of a picture posting, but in my experience pictures are far more useful than words anyhow. They are big and numerous, so if you live in the stone age and have 56k, just hit the back button now.
My lower back was sore after driving normally. I have a rather huge butt compared to my 'lumbar' area, and the seats in my STi really have the opposite support (big bump for the butt, and nothing for the lumbar area).
I started by taking the whole 'grid' out of my seat. If you aren't familiar with the mod, it involves unhooking a springy grid support from your seat. There are three hooks on each side. I didn't want to just unhook one side which appears to be common. Please, if you do this, wrap a cloth around what you can when removing it. There are a lot of non-interior-friendly hooks to rip your seat otherwise. It wasn't much harder to just remove and put back in if needed, and doesn't risk ripping the seat. This really changed the feel of the seat, and I would recommend anybody do this before bending the grid around at all. It gives you an idea of what you have to work with. There is no longer that obnoxious butt bump, so you can now sit comfortably into the seat. The thrill of having side bolsters was there for a bit... until I realized they were angled out too much to help anyhow. And then I was left with a big bucket shaped seat. That also bugged my back, but on the upper part of my lumbar instead of the lower. I also felt like I was a hunchback.
A week later, I returned to this semi-evil grid. With pliers. Two big ones. I unbent the bottom two rows a bit, left the next one up as is, tightened the one above that, and then loosened the rest up to the top. It no longer sat flat on the table, and almost resembled something that looks form fitting to me.
Results: I am very pleased with the bent grid. I may go in and tighten up some rows above the ones that I left alone. I feel that I could use some more back support a bit higher up than I gave it. Also, I may pick up some surgeons tubing or rubber and experiment with that a bit. It may provide a much comfier alternative. Could always cut some stretchy fabric in a peanut shape and sow it on as well. Who knows. If I do that, I may get creative and cover it with semiconductor heat transfer crap (no joke). That fabric is great, but some cooling would be awesome. Bottom line... I'm pleased with it, but there is potential for much better. I am going to look into my seat cooler idea.
Pictures: I'm not going to caption these. I tried to get a lot so you knew what to expect. Take note that there are 3 clips that need undone on each side. Some of them are before pictures of the grid, and one or two are afters.