Gotcha, Dave. And I know that you have a good sense of what is going on with your body. Of course it makes sense to me that you do need to maintain a certain "suppleness" in your back but you do not want to give up stability. If the hips are tight relative to the lower back then the back takes over range of motion resulting in a lack of stability in the lower back, hence, the entire core, and hence less than optimal strenght and power. I know that it is a fine balance and tradeoff. Definitely something to think about though.
I've had some pretty bad back problems that I've been able to improve greatly and one thing I can say is that for a long time I thought of my back being "tight" because it "felt" tight. What I figured out is that the tight feeling had more to do with neural response becasue of my back having to take over range of motion in a loaded environment. My back was "tightening up" but that didn't mean the problem was in the back. So as I really started to focus on hip mobiltiy, ankle mobility, upper back mobiltiy and core stability my back problems really started melting away.
Of course you can rightly say that I'm not doing MMA
. So take everything with a grain of salt. But I will say that all those very dynamic things, and odd implement things, olympic lifts, etc...that used to give me such problems are becoming more and more a walk in the park.
I think a lot of people believe in this myth about the lower back "locking up" if you don't stretch the hell out of it. But everything, when it comes down to it, is about "mobility" I.E. not how much your muscles can elongate or go past a set tension point but about how much dynamic range of motion you have...i.e. useful range of motion where strength and control are on par. I could be wrong, but my sense it that everytime you do grappling and things like that your lower back is getting a mobility workout. My honest opinion is to focus on hip, anke, and thoracis mobility.
And in case I don't say it enough...great stuff!