Okay I found a way that works for me. Including it here for anyone that also finds it hard to get seamless audio files.
-Do not convert your wav file via C2. Open it in Audacity instead.
-Once open in Audacity, go to Effects>Repeat. This will add a 2nd version of the audio this way you can check the seam.
-Edit the audio file down as needed to make it seamless. Once satisfactory, delete the repeat.
-Export your audio as an AAC file and as a OGG file.
-Import each file (should be 2) to C2 in to the sounds folder. No conversions should happen at this point since you already are supplying OGG and ACC/M4A files.
This seemed to work best for me. Exporting to AAC via Audacity does add a small gap but C2 seems to ignore it while in the Sounds folder.
**Note**: When you download Audacity, you also need to download the codec/plugin to export AAC files. The program will let you know if it isn't installed and provide a link.