look for a Zip Fit dealer to start. The problem with mine is that they are silicone injected which translates into not working with any other shell. The new Zip fits are a cork material that forms to your feet each time you wear your boot. so as long as there is enough room in your boot shell to accomodate a liner, you will have a custom boot each day.
If you can find a silicone injected liner they are the bomb.
The problems are;
-the liners will outlast your shells
-as the size of your lower leg shrinks because the liners were fit for lower legs that ski 70+ days per year, they do not fit any more. I only get out 20 - 30 days anymore and being a desk jockey doesn't help to keep me in shape.
If one skis/boards similar number of days per year silicone injection is the way to go. if you are not consistent in your days the cork liners or remoldable liners are the shiznit. I think that Zipfit has discontinued the silicone liners, but some dealers still have some left. The guys that fit me are pretty bummed that silicones are no longer available.
A ski boot liner will definately add stiffness to any snowboard boot on the market, just know what you need.
http://www.zipfit.com/