As you probably know by now, my web page has some descriptions on altering fit through insoles, which likely covers cramping issues. I've recently been experimenting a lot with warmer insoles. I want to play a little more before finalizing this on my website, but here is where I am so far:
Here are the things I am experimenting with, to make my boots warmer:
1. If the boots can be heat molded to fit you better, do so.
2. Pick a good thick (as thick as you can - this helps a LOT) foam insole as a starting point. E.g., the $4 bi-layer Dr. Scholls from the drug stores. The materials that most of the really expensive insoles are made of are lousy thermal insulators, and have no advantages that I can find. (Exception: molded insoles, including the ones that many podiatrists use, are faster to fit. But they probably aren't very warm.) (Foam, especially closed cell foam, is close to the best insulator there is, way better than leather, rubber, solid plastic, wool, etc.) Do NOT pick an insole that says "cool".
3. Adjust fit (at high pressure points) by cutting away parts of the lower density layer (the one that has bigger air bubbles), not by adding tape. At low pressure points, add more foam, not tape. On my web page, I said to use tape, which is easier and faster, but foam is warmer.
4. Make sure your insole covers the entire bottom of the boot, including toes. An uncovered portion leaks a lot of heat.
5. Likewise, fill the toe end, just beyond your toes, with foam. Open air spaces there loses you a lot heat, due to "convection".
6. If the sides of the boot near the bottom aren't tight against your foot, oversize the insole a little so it climbs up the sides of the boot a bit.
7. I am currently experimenting with adding an aluminum foil reflective layer under the foam, cut to the same shape as the insole. I won't go into the physics, other than to say it is an infrared radiant heat reflector. I didn't think it would help, because the foam insoles are white (which is somewhat reflective and tends to suppress radiation anyway), and I am still experimenting, but I think it may help.
8. Warm your boots to about body temperature (98.6 deg F or 37 deg C) before putting them on. Use a rest-room hand warmer, a hair drier, or a microwaved sock full of rice in your boots. This is huge.
9. Consider neoprene boot covers.
10. I may give up on hand and foot warmers. Better insulation works better for me - but for people with extremely poor insulation, they may still make sense.
11. Skate at rinks with warmer ice and warmer air. Don't skate outdoors.
I'm sometimes breaking those rules - which is the reason I'm working on making my boots warmer.
Stay warm!