OldSteve,
Sending chip select twice seemed to provide the time needed for the MAX31865 to do it's thing. I got that code working a couple of years ago and have not messed with it since.
J-M-L,
To be honest, I got the conversion code from Hani, an application engineer at Atmel, for a project where I had 15 of these chips on a board, and it worked well. I've tweaked it to output degrees F instead of C, other minor things, but left the basic conversion and error clearing alone. Looking at page 12 of the datasheet, looks like 500-600uS, not mS, are all that is needed. I can play with changing those numbers, see if I can detect any difference in the outputs from the chip.