S Aare, S Crimsonette, S Pacific Country Cousins, S. Rubra Ash, S. Emerald Evergreen, S Commander Haye all can get to 8". Sources are easy for most of them, Aare is from Edelweiss. I think SMg has most of them. Growing conditions can have a big effect on size. If you want large ones, transplant a young rosette to a private spot. Semps appear to communicate with each other when growing in a clump to keep the sizes down.
J. heuffelii Fandango is the largest heuffelii I've run into. Easily 8" or better (that planter is 8" wide shortest dimension)