Hmm. I've been going with BTB and just under 50 ppm Ca, and though I said no problems have surfaced, the beers HAVE been slow to clear. 50ppm should be sufficient for clarification (and oxalate precipitation) but if it's down to 30ppm, that could have an effect. Think I'll skip the BTB this week and see if the beer clears any faster. The faster it clears, gets tapped, and gets consumed, the less the concern about long term oxidation effects!
Heck maybe I'll skip the Irish moss too, and see if extra trub carryover really speeds up the whole process. Have seen suggestion to that effect.