My wife uses the 4R to work everyday, I drive it once every month or so just to check any issues, engage 4wd etc., I've noticed the drivers bottom seat cushion is not level, the left side is lower than the right side: I have noticed this in the Hilux too. I fixed the hilux's driver seat few years ago and did the same for the 4runner.

The issue is the spring/steel wires on the seat bottom frame have cut into the sponge/cushion. The fix is to add a thin plywood sheet between the cushion and spring/wires. This made the seat bottom to rise up about 1/2 inch or so and improved the visibility due to the higher seating position. A bonus is now the window line on driver's door is below the shoulder, and has given a truck like driving experience!

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you might like to drill some holes in the plywood to allow the foam to breathe.
otherwise, you'll end up with a sweaty butt even with the aircon on.

My fix consisted of 2 pieces of spare carpet floor mats (from VW and Toyota, in this case), shaped to fit inside the seat bottom side bolsters, covered by a thin cloth seat cover(which I use anyway). The Toyota OEM foam, which I bought a new copy of, was just way too soft.