Adobe DNG Converter creating very large files

[Sponge]

I just converted around 500 RAW files from an Olympus E-PL2 using the DNG converter (v6.4) and the vast majority of the resulting files are around 50mb, give or take, when the original RAW files average 12-13mb. At first I thought maybe it had to do with me having the preferences set so the files work with an earlier version of ACR (v4.6) but I noticed that some of the files,though very few, came out to be 12-15mb. I don't have the preference checked for embedding the originals so I'm really stumped on what can cause such a huge increase especially since it doesn't affect all the files. Any ideas?

[Sponge]

Never mind, it is indeed caused by the preference being set so that it can work with ACR v4.6. When I switched that setting to ACR v5.4 the files were around the same size or a little bigger with full size JPEG Preview. It turns out the smaller files were from the pics I took with an old Canon FD lens. Apparently the current micro 4/3 AF lenses need an extra 40mb of space for the file to be backwards compatible! This might motivate me to use my MF lens more often.
I guess I should have done a little more testing before posting on here but the huge difference in file size threw me for a loop. Oh well, maybe this will serve someone else with the same problem.

[Donald]

... maybe this will serve someone else with the same problem.

That's the value of it being here now. Glad you found the answer, Patrick.