For me, a 6'6" monster, the killer was the angle my right ankle had to be at to work the pedals with my leg bent to fit on either side of the wheel.
Ended up doing a few things, and here's what I figured out:
1. I made some risers/extenders for the rails, like Oldwineo, but with (I think?) 1" square tube instead of bar stock and stacked washers. This got me 3-4 more inches of back travel, and an inch higher seating position. This helped a lot with basic comfort, but I still got a sore ankle in stop-and-go traffic.
2. I swapped out my stock front seats for a pair of 'Turbo' JDM seats. Thinner, higher density foam, and just in better shape than my original ones. This helped a bit, but since they were from a RHD truck, the more adjustable seat is on the passenger side. This led me to experiment and realize that the tilt of the seat bottom, not just its position, was important, so....
3. I made spacers out of 2x1/8" bar stock (3" long rectangles with a bolt hole in each end) that effectively move the front floor mounts up 2", which the brackets easily flexed to accommodate. This way, my right leg is supported by both my right foot *and* the front edge of the seat instead of just being held up by my foot. At first, it seemed a little chintzy, but with the beefy m10 bolts torqued down with lock washers etc., it might as well be welded for how solid it feels.
Plans for the future are to replace the square tube risers with flat bar, because the 'lift' ended up being way less important than the tilt and extra couple of inches of effective rail-travel.
Fun fact: fairly short adults can still juuuuust fit behind me comfortably.
