I started, but never completed, an attempt at a 8-day clock. I was able to get the escape wheel to begin rotating from a dead stop with 4 coke cans as weights (~3.5 lbs). I was figuring on having to double the weight to drive the pendulum, so was figuring on 7 lbs total. In a separate thread I seem to recall you indicating that to get the desired drop, you were going to introduce a pulley, which would effectively double the required weight, so maybe 14 lbs is in the ball park?! Again, I never completed my clock. (One of these days!)
If I was in your shoes, one thing I would consider is to have a pair of 7 lb weights, with the chains coming off the great wheel horizontally. I believe this would provide 2 benefits: 1) helps counterbalance the load on the great wheel arbor, reducing wear and tear on the bushings, and 2) a pair of 7 lb weights are probably more aesthetically pleasing than a single 14 lb weight. Of course, this introduces the complexity of 2 ratchets and barrels on the great wheel arbor, and possibly another set of small auxiliary pulleys to aid in wrapping the chain more completely around the barrel...