I was looking for the IOR for latex earlier today, seems to vary from what I found, between about 1.42 and 1.59.  I was playing with one at an IOR of 1.5 (splitting the difference).  Think I need to bring the roughness down a bit but am getting close.

Mind you, Laurie is far more familiar with how materials go together and would probably get it done much faster than I will.  I admit I am still plinking away trying to figure out what everything does in the various materials definitions.