PC Engine & GBS-8200 - Sync Solution?

[SmokeMonster]

I installed broken's RGB amp in my Turbografx-16 and am having trouble getting it to work with my Gonbes GBS-8200 w/LM1881 sync stripper. I'm looking for suggestions from anyone who has managed to get the PCE/TG16 to cooperate with a GBS.

I added a switch to my GBS to allow me to bypass the LM1881 for testing. I've tried all of the following sync solutions with both the LM1881 circuit present and bypassed:
1. Composite video from the ext
2. C-sync pulled from the hu6260
3. C-sync amped with the traditional 2SC1815 amp
4. Luma pulled from the hu6260 (the LM1881 can extract sync from luma)