When skiers have a problem with a boot being too tight, it is often a bigger problem than a simple heat molding of the liner. Because plastic shells are rigid and unforgiving, the best answer can be to modify the shape of the shell. Here is some of the equipment we use for this work.
Our newest - and possibly favorite - punching device is this Tecnica press. Designed by Bart Tuttle (recently retired from Tecnica, worked on World Cup with Pat), it features a lot of advancements from the standard boot punch. First among these advancements, is the moveable punch angle. Rather than only allowing straight punches, it can be turned so that areas such as the 6th toe and bunions can easily be reached with the press. Other features include a digital gauge for measuring the punch distance - allowing greater accuracy, and the built in timed heating unit.
We have a number of Scott presses, which have been the industry standard since the mid 70's. They can produce excellent punches, with the only negative being they are not as good at punching the front of the boot as our new Tecnica press. Punches generally take about 1/2 an hour each, and must be done in succession. Because we have a number of these presses, we can usually perform two punches at a time.
This Ultracam is an $8k piece of machinery and is the state of the art for making large stretches to the whole side of a boot. It also works well for stretches for widening the curve at the front of the toe box. Stretches of over 20 mm (3/4") are possible, which can be very helpful for skiers who require a boot that is far too narrow for them. The process is time intensive, and usually requires overnight pickup.
Widened Nordica race boot by 20mm (3/4"), performed with the Ultracam.
Your feet! Sometimes the best way to stretch a boot is by heating the shell, padding the problem foot areas and then having the client wear the boots for around 15 - 20 minutes. How successful this will be depends on what type of boot it is and where the client needs more room, but clients are often astounded at how much better their boots fit with this method.
While a number of brands design their boots to be fitted this way (Salomon, Atomic, etc...), most boots can work with this method in the right areas.