I recently converted from 6:1 to 7:1. It was really easy to do, I just added a spring supported block where the sheet used to finish on the bottom block, and attached the sheet to the unused bracket on the top block. I had to get a longer sheet however, but I reused an old spi sheet I had.

7:1 is better than 6:1, I can get it tighter with one hand that I use to be, and that's an improvement upwind. I think 8:1 would be too much rope to pull. I'm now going to reduce the amount of sheet needed by making a tail to lower the top block and then probably make a taper.

I made myself a poor man split tail (a dyneema loop on one side, the traveler line goes through the loop and attach to the other side). To have the car not move at all when you sheet in was a good improvement.