My cone 6 porcelain isn't translucent - just very white (It's from Tuckers - called Bright White) and my cone 6 black clay is very sturdy - never warps, which is why I love it so much. A gorgeous clay to work with (although impossible to get glaze color on unless it's blue or red - everything else goes clear or horrible mustard!).
In any case, the biggest takeaway from all this advice is...as usual... test!
But I'm glad to have all these comments. It will inform my testing. I'm always trying to get away without testing, but it's no use!
Thanks everyone. My work is almost dry - I will reserve one shelf in my glaze fire tomorrow for testing these ideas..