Joe,
1.78g is probably too light. It's certainly too light for the higher end ZYX's, and AFAIK the suspensions are similar. I fear mis-tracking on dynamic passages, if not now then certainly when cooler weather arrives.
1.90g is about right in the summer and I'd probably want to start a new cartridge off a touch heavier than that. In winter you'll probably want to be closer to 2.00g.
You either need a lighter counterweight or a headshell weight. The fancy ZYX's have an optional headshell weight that adds about 4g. It is useful on all but the heaviest tonearms. In addition to giving you a more useable VTF range, increasing the system eff. mass should improve bass and dynamics a bit, sort of like the HIFI mod does.