Hi Kent
The Ikelite website is apparently silent on whether a dioptre is needed or not. Some lenses are annotated with the indication that a dioptre is needed, some are annotated with the indication that a dioptre is not needed. This leaves you either assuming that this means a dioptre is not needed, or that the lens has not been tested by ikelite, which seems unlikely, on the basis that they seem to have specific results for most other lenses.
The 6” ports generate a virtual image at around 30cm from the port, so if your 14-42 is capable of focussing on an object 30cm from the lens (or closer), you should not need a dioptre.
Hope that helps