Mash out at 75 but heat sparge water to 80 and adjust pH to 4.4. The sparge water sits on top of the mash for a while before it runs through so it could be even warmer.
Reading a good book at the moment, I am more into mechanical engineering and this is written by a biochemist so leaving me all over the place regarding the best practices in brewing, but he does suggest 73 to 75 C and a 60 to 90 minute sparge.