Gave my AT boots a stiffy.

I loved the fit and comfort of my Lowa Strukturas, but they were pretty wimpy in the flex department, even though they are a rather heavy boot.  Had one of those wake up in the middle of the night ideas that turned out to be right on.  I have Dalbello Kryptons that came with two sets of tongues.  I am using the softer ones, so I took the stiffer set and replaced the tongues on my Stukturas.  They fit great, and are a bit taller and way stiffer than the stock ones, and fit close enought to be water tight so far.

Almost all of the AT boots that use a 3 piece design will accomodate Flexon tongues. This is a really common modification that people looking for a stiffer flex will do, but it can make the uphill a bit less comfortable. I have the Strukturas, too, but my problem with them is that I need a narrower, tighter heel pocket for my skinny ankles. As far as the weight, have you switched to Thermofit (Intuition) liners? I must have dropped a pound per boot or more when I did that, and they are incredibly warm, too!

I got a screaming deal on my Strukturas because it was the last model before then went to thermofit liners. I tried to use the liners from my tele boots, which would be 3/4 lb. per boot lighter, but they are not the right size.  I guess I will have to suck it up and spend the bucks for Intuitions.

The Strukturas had a reputation of being the most comfortable boot for walking and climbing, which is what I found, but at this point I'm willing to sacrifice a little comfort for better ski performance.