With only 3 division opponents, I can see where intradivision games are hard to come by. There is one schedule of that configuration in the "Import into OOTP6" thread. Of course you'd have to be careful with backing up, etc, etc, but I think since you can copy the Stickware created schedule.dat files into V4, V5, V6, it seems like it would be possible to import a csv-format schedule file into V6, then copy the resulting .dat file into V5. In fact I just tested it and it worked, at least the schedule appeared and everything looked fine like when copying the .dat file from Stickware. If you do not have V6, I could post a copy of the .dat file in a .zip file for you to just copy into your V5 league. {EDIT: This may not be quite so simple, as in my test it was the same league I constructed in V5, imported in V6, imported the schedule, then copied the .dat file back to V5. The .dat files may not be able to be as generic as the new csv files may be for V6. But it can work one way or another though it my take you sending the .lg folder to someone to import into V6, then them importing the csv file, then sending you the resulting .dat file.}
Anyway, check out the details for that schedule linked in the first post.
Actually here's a link to it. I believe the only Sept intradivision games are the last 3 series are against the other 3 division teams. That is a league configuration for which I have a league I plan on playing soon, and that was one of the first schedules I made myself, so I've been thinking of doing another for that set up anyway. If another distribution of games would be preferable to you, describe it and I may give it a whirl. With my experience and that not being too difficult a configuration to work with, it would probably be relatively easy for me to make one.