I don't know what's best, and I'm not sure how accurate that article really is, but pull ups at 250 would be significantly harder than at 200. Your best bet might even be to do realy heavy pull downs for now and low sets 3-5. Once you get to 225 may be a better time to do the progressions?
I have a feeling what you are feeling in your shoulder is more a case of early biceps tendonitis and not a shoulder impingement. Usually this flares up when you add significant amounts of the rowing motion.
I am also not really a big fan of the progressions. I think doing heavy pull downs, heavy single arm DB rows and weight loss are more effective than anything else. And honestly a pull up is just a pull up. Its really not that big of a deal. I actually like the feeling of a pull down better than a pull up. It feels safer and more effective of a back workout. If I had a pull down machine I think I would do it as much as I do pull-ups. I think the stabilization piece is a bit overkill, and there is no way it is a more effective lift than say a farmers walk, DL, Goblet Squat or leg raise.
So honestly my advice would be to dump them for now and focus on other things. I really think at 225 or less you will have no problem knocking a few out.
Thanks, since writing that last comment, I've been thinking the same thing. It really helps to get your feedback and additional insights. That tips the balance. I've always done well with pulldowns, and like you say, I like to do them in the 5 rep range, fairly heavy at around 170 pounds or so. I could do them off the floor, kneeling so if the loaded weight starts to approach my body weight, I'll rise up.
I did 240 bench press yesterday, no problem, so the basic program I've been pursing is leading to good results in all the other lifts. As you suggest, I think I'll just put chinups on the back burner and trust that they will come as my general strength levels continue to improve, and, hopefully, as I lose some of the excess weight I'm carrying. My wife says my butt and back are getting bigger, so I'm doubting that 200 is realistic for me, but something like 210-220 is probably pretty close to my lean BW. It's hard to say, but it appears that the last several months of deadlifts, rows, and squats have added 10-15 pounds of mass.
I'm also concluding that what I'm dealing with isn't shoulder impingement. But the funny thing is, it moves around, so I wonder if it's any one thing at all. It could just be trigger points/knots resulting from a lack of mobility and/or post workout stretching/massaging. Right now where I'm feeling the most pain is at the top of my triceps, where it meets the shoulder, maybe the lateral head? A month or two ago I was feeling it in the anterior delt and pec. I've been stretching and massaging it quite a bit over the last 48 hours, and it's helping quite a bit. Yesterday on the bench press I didn't feel anything at all, and the day before, on the deadlift, although it was quite painful, it didn't interfere with my ability to go super heavy. So I dunno. I'm doubting it's anything structural. Plus, it was actually worse before I started getting back into shape. It would make a clicking sound.