Interesting info about plugs, guys, but my experience has been quite different. Let me explain, where I am coming from. I am on a budget, so I shop for deals and wait to buy most of my equipment till I can get a discounted price. My current Lange RS140 boots were bought off Ebay for under $300. They were used 1 or 2 times and were too small for the owner. His loss, my gain. They have been almost perfect for the last 4 years. I did go to a shop and try on a couple of boots to make sure I new my size in the RS series quite a while before I found the Ebay add. I didn't spend much time getting fitted, however, because I new I wasn't in buy mode.
First question I would like to ask is "do any shops stock plug boots?" I don't know of any, but I haven't gone looking either. If they don't stock them, then is a shop willing to order 2-3 different sizes so you can shell fit them and decide what is the best size to start the work on?? I would assume for a ordered plug boot, you are going to pay the "high season" price, which is typically around $650 for RS boots. Then, if I go with Bogy's approach, there is the cost of a new liner. That is probably needed even if you don't follow Bogy's approach for me just because a liner that fits a 28.5 shell will be too short for me. I will need 29.5 liners to fit my foot. Or I will be paying to modify the liner as well as modify the boot. I would roughly expect the whole thing to cost around $1200 when as is said and done. That's about a 4X increase over my last boot buying experience.
Now for that money, I will be getting a lot more boot/liner/fit. It sounds pretty good to me, but I have to be able to afford the $1200 and the time at the fitters. I don't have a fitter near me, so its at least 1.5 if not 3 hour drive to a good shop. I suppose a "race shop" would have the whole process down pretty well and it wouldn't be too stressful to go through.
I do realize since I have a narrow foot, I can get away with an off the shelf boot without pain. This streamlines my experience compared to most peoples. I consider myself lucky to get away with my Ebay approach, but it worked for me. I also always ski Langes, so I know how they fit my foot (quite well, although I trade length for snuggness, never any pain).
One other comment about the flex of the boots. Again, this maybe specific to my size boots, but when I took both screws out of the back of my boots, it had a minimal effect. The rear section of the lower boot is so high and stiff that it makes very little difference whether the screws are in or out. The major factor in my boot flex is the 2nd from the top strap/buckle around my ankle. The strap sits right against the lower shell and prevents the upper shell from rotating. To flex the boot, the lower shell has to deform and flex outward. Its pretty stiff and doesn't deform much when I have them buckled at my normal (tight) position. Maybe this is how all boots are, but these are stiffer than any other pair of Langes I have owned, of course they are the first pair of 140's I have owned. I was told the 2012 RS140's have stiffer plastic by Jim at the Start Hause. I have been in and flexed both the RS130 and RS140 and I believe he is correct. That may have changed over the last few years??