I've knitted 77 rounds so far in Beaverslide McTaggart Tweeds. I just added my third 4.5oz skein on round 76 so I think I'll have enough to finish. It should last until round 89 according to my calculations and there are only 87. It's getting really big! I have about 36" so far so it will finish at maybe 42" unblocked.
I would recommend doing this in Eco, Beaverslide or another heavier weight yarn instead of worsted because it's a lovely textured pattern and it goes so fast! I think this will end up costing $27 to make, which is awesome for a lace blanket.
I'm hoping I can finish and block this weekend!