I knew where you were coming from on the "enough" thing and I agree with you on that stuff - it's just always interesting to talk about and kick around...what motivates us, what makes us feel good or bad, etc. How should we look at life? You know...all those philosophical questions.
Yeah, I would think two dumbbells would be safer - getting a broken rib from dropping a dumbbell that just slips would be a lot worse, IMO, than a pulled muscle. But, I get experimenting too...
As far as me...my progress is SUCKING. I have been doing the 6-week pull up challenge and making some progress there. My life has taken over lately, which is a bit of an excuse, but I've been focused on making some $$$ and getting things geared up. I've been going in 3-4 different directions and the dieting has taken a back seat, kind of. I'm maintaining around 190; which is good - but I need to take off about 30 pounds again.
The theory behind negatives is they induce mechanical damage to the myofibrils in the muscles. Think of the muscle fibers like a ratchet, the fibers contract and lock into place with the teeth interlocking into each other - as you force the muscle to extend, these teeth slip past each other and get damaged, which triggers growth.
This means that having a completely locked position that turns into a controlled negative will theoretically inflict quite a bit of "damage" and trigger a response. However, in this case, he is trying to hold a locked position and has trouble achieving it and adding weight will only make getting that locked position even more difficult.
Aren't you the one that always talks about more reps and lower weight contributing to muscle the same as heavier weights? Now you're telling him to add weight to a movement he is already struggling with? Give the guy a chance!!