http://yourserverip/fmi/webd brings up the webdirect home page.
http://yourserverip/fmi/webd#yourfile is a direct link to your file.
I would use the GetThumbnail() function to store a web-sized image in your database of the original image. This will help with consistency as well as dealing with your variable sizes. In terms of rendering speed, as long as the files are hosted on a drive on the same server (and not an external drive that needs to spool up), then you should see no difference in rendering time. All WebDirect views and data are rendered server-side and then sent over to the client.
Many thanks Mike. I appreciate it.