I did 20,000 road miles in my last 7 (K series with standard road springs) with approx 85mm under the sump with me in the seat and I don't remember ever scraping it. I'm aiming for 90mm in my Sigma car.
Remember putting my 420R with stock suspension on the ground for the first time, it was a very low, but looked fantastic. I used the ride height settings from the old build manuals, which covered the 420R, for the drive to IVA, and the running in. The intention was to get a flatfloor at 1000 miles, but other things have taken focus so it's still on my todo list.
My detailed build blog