Yes, it is. I did this before I opted for a used drum scanner.
You need the 6x12 Flextight film holder. Simply scan one side, then the other. Ensure you overlap quite a bit. Keep all settings the same for both scans.
When you have completed the scans, you need to stich them together. you can do this in Photoshop, but a better way is to use a tool designed for this purpose, and one of the best (at flat stitching like this particularly) is PanaVue Image Assembler.
You should get near seemless results. It is a bit of a kludge, of course. In the long run, if you do a lot of 4x5, you might be better off with the Imacon Precision or a used drum scanner, like the Howtek D4000 or 4500.
Quentin