I may make shampoo bars at some stage; unfortunately, natural soap such as I make, is too alkaline for hair. That's probably the problem you've had flip-68. It leaves the hair stiff and not shiny - not a good look or feel. The only way around that is to rinse with a vinegar solution afterwards; this brings the Ph back down. I've done this today and it worked fine; the vinegar smell disappears as the hair dries; I used about 1/3 vinegar to water, and sprayed it on from a spray bottle and left to dry. It left my hair feeling pretty good, so I'm going to continue the experiment for a while and see how it goes long term.
However, I'm aware that most people might not want the hassle of spraying with the vinegar (although it's no more hassle than using conditioner which I usually do, and my hair feels possibly better than usual).
Shampoo bars that leave the hair feeling o.k. without using vinegar or something similar, will be made primarily from synthetic surfactants. But at least they avoid yet another plastic bottle.