Have you tried on 16's at all? You're taller than me and I was wearing (tight) 16's at 225lbs so they might actually fit pretty soon for you! After that it really depended on where I lost weight. I was in tight 14's before I hit Onderland so it was about a 20-25lb difference. I was in 12's in the low 190's and now I'm in 10-12's in the low 180's (in the last 10lbs I haven't lost much around my bust/waist/hips but rather my arms/thighs/face/back).
So, yeah, I think maybe 20-30 per size in plus-sizes and then roughly 10lbs for non plus-sized clothes. I like to track my measurements so I know where I'm losing so I don't get disheartened if I'm not dropping clothes sizes as quick as I'd like. For instance, right now you might be losing a lot in your arms/back/neck/calves/thighs etc but not in the mid-part of your body, which is what allows you to drop a size.
BTW, good job on your weight loss, I'm sure you'll be seeing the next size down soon!
