My HTTP and HTTPS servers point to different locations, should I install two copies of X-Cart, one for HTTP and another for HTTPS ?
This can be done, but keep in mind that you will have to setup both of them separately or, after setting up one X-Cart, copy it to another location. However, this method has a lot of annoying side effects. For example, you will have to maintain two copies of templates. If you edit HTTP templates, you will also need to edit HTTPS templates in the same manner, i.e. you will have to keep both the copies synchronized. Much better if your HTTP or HTTPS server allows for symbolic links: you will be able to keep only one copy of X-Cart directory, while on the other one there will be just a symbolic link to it.
*Sadly, we had to bring back ads too. Hopefully more targeted.