Any drawbacks to passing audio through ES15 as well?
 

My setup for capturing PAL Hi8 is:
Sony CCD-TR825E (TBC On) --S-Video--> ES15 --S-Video--> AVT-8710 --S-Video--> Pinnacle 710-USB --USB--> Windows XP/VirtualDub

The audio, however, goes straight from the camcorder to the capture card:

Sony CCD-TR825E --Component Audio--> Pinnacle 710-USB --USB--> Windows XP/VirtualDub

and is therefore three to four frames ahead of the video. If I route the audio through the ES15 as well, this difference disappears (which saves me some extra syncing steps). Is this detour harmless for the audio?

If not, can I use FFmpeg to delay the audio on the AVIs, or are there better alternatives for doing this?