I got that problem A LOT too. Sometimes the cramping was so bad it would almost ruin my day because I would have to take a break and take my boots off. To me it usually happens the worst when the boots are new and I cranked them down too hard. I have super flat feet too, so I would sometimes even put a different footbed into my boots to help with relieve some of the pain. Footbeds definitely help, but as someone mentioned above, sometimes I ride a few runs early with them loose, then start to crank them down as my feet get warmed up and used to the boots.