Along with the work described on the other post on insulation, I decided to move my butt vertically. On a good day, before getting beaten down, I stretch to 5'6".
I took a length of 1.25" steel rod, cut 2 lengths and machined them each to a length of 1.5". This is bored through with a 0.335" drill followed by tapping to match the rear seat bolts: M10-1.5. This is threaded over the seat bolts until they are snug against the floor. The seat rear brackets are rested on top of these and corresponding metric bolts are threaded into the tapped rod. This is about as high as you can go without serious interference of the headrest and the headliner. I originally had it at 1.8" but this gives more movement. The drill is not the correct one, but I didn't have the 8.5 mm one. This is a hair bigger, but does the trick. Don't need a booster seat any more
I took a length of 1.25" steel rod, cut 2 lengths and machined them each to a length of 1.5". This is bored through with a 0.335" drill followed by tapping to match the rear seat bolts: M10-1.5. This is threaded over the seat bolts until they are snug against the floor. The seat rear brackets are rested on top of these and corresponding metric bolts are threaded into the tapped rod. This is about as high as you can go without serious interference of the headrest and the headliner. I originally had it at 1.8" but this gives more movement. The drill is not the correct one, but I didn't have the 8.5 mm one. This is a hair bigger, but does the trick. Don't need a booster seat any more