I waited until I got a couple powder days in my RX 130s before posting. Now that I have I can say that mine haven't leaked a bit (he said, knocking on wood!).
I'm skiing the 100mm last with the stock liners and custom footbeds moved over from my previous boots. The lower half of the RX 130 happens to fit my feet extremely well. No punching, grinding or stretching required and I don't anticipate much, if any (unlike my old 98mm Banshees, which needed quite a bit to avoid crushing my 6th toes and inner ankles). I'm lucky, and happy, that Lange decided to make a boot that fits my feet.
My toe buckles are tightened only enough to stop them flopping open. My instep buckles are snugged just a bit more, 2-3 turns of the micro-adjusters. This creates the tiniest bit of shell deflection, which is all I need to get a good fit there. (I have slightly but not super high insteps.) Perhaps the overlap doesn't leak because I'm not deforming the lower shell much?
The cuffs are another matter. Nobody makes cuffs small enough for my skinny calves without cranking them down, so I was glad to see Lange made it easy to move the cuff notches to their tightest position. The buckles are in the second notch with the micro adjusters about halfway. From experience, as the liners break in I'll slowly tighten the cuff buckles more and more, but there's a large adjustment range and it'll be a long time before I pack these liners out to where it's a problem. Importantly, compressing the cuffs to fit my ankles and calves does not seem to alter the shell around my foot. That's very good.
As good as my Banshees were (skied 'em for 10 years) the RX 130s are WAY better. First, they fit almost perfectly OOTB. That's just luck but it makes a huge difference. I have ample toe wiggle room and no excess pressure on the top of my foot, but from there on back and up the cuff these boots hold like a vise (without any pain). The heel hold is absolute perfection. Since I have no natural padding over/around my skinny shin bones I do have to pay close attention to cuff fit. If the buckles aren't snugged exactly right I get pressure points at the tops of the cuffs (especially on my smaller, R foot). Snug the 2nd buckle just right, however, and it pulls my heel back and gives me a consistent, tight fit from the ankles all the way up to the strap. No pressure points, just super ski feel and iron-like control.
The upright stance is a big improvement for me. I'm much quicker in the bumps, stronger on high-G carvers, more confident on ice and less fatigued overall.
About the flex... I'm 5' 10" but really skinny, < 140lbs. The flex with one bolt removed from the rear cuff seems perfect for me (removing both bolts made the boots too soft). I pounded big bumps last weekend to see if the boots would throw me. Not only did they NOT do that, I've never skied bumps better. I was on top of every turn and skied more aggressive lines than I have before. For me, these boots are fast fast fast and rock solid too. I know what's happening down there every second. Not quite a race boot, but I'm not quite a racer.
On stiffness alone I could have gone for the RX 120, but I really wanted the replaceable heel and toe pieces (which really help when walking/climbing) - and you gotta love that GREEN.