Hey Guys,
So I used Zip Fits for most of my career in NW .950, and UPZ. I like the World Cup/stiffest version the best and I would soften the boot to get the stiffness I would want. (You can always make the boot softer but it can be difficult to make one stiffer)
For molding I would use a hair dryer to heat up the inside of the liner and then while hot place my foot in the liner then the boot and then allow to cool.
When using this liner you always need to put the liner on you foot first and then step into the shell. If you don't the cork and silicon gel that is inside the gel will move to the bottom of the liner and no longer give you the support. These liners are made to always slightly change with the heat of your foot while in the boot to get a perfect fit. So in essence they are "always" being molded. I have been in a jam a few time and have just put an fresh new liner on and ridden it straight out of the box and after a few runs they are good to go and comfortable.
In my experience I have found that the is a fine line between to stiff of a boot for a person and to soft. A stiff boot will give to lots of leverage on the board and will allow you to rely on the cuffs/tongues to support you in the turn. Now on the other hand this will give a rider the locked in feeling and they will not be able to have much playfulness in the turn. A soft boot will allow you to have all the playfulness in the world and the big bumps will feel like nothing. But you turn will feel blah with no real power in them and you will have a little bit of the out of control feeling.
Everyone has the own opinion of what is best and everyone will have a different set up. Its all about what works best for you.
Hope this helps!
Mike Trapp