If you get the error Could not load type from assembly ‘System.Web profile when doing something like a unit test and trying to make a profile, you probably need to add the assembly name to your class declaration.
eg, using System.Web.Providers and the new inherits feature to specify your Profile:
<profile defaultProvider="DefaultProfileProvider" inherits="RationaldDev.Models.Account.MyCustomProfile, RationaldDev.Models">I had some problems with the Logitech MX Master 3S Mouse with an M1 MacBook Pro, but I had better luck with a Logitech G502 X Mouse