Clay won't keep the heat off the S-7 any more than it keeps heat off tamahagane. The clay impedes cooling. I doubt it will impede cooling enough on S-7. Unless it takes more than 75 seconds to get down to 500F, you miss the bainite nose.
I would use the kiln to anneal, and I would HT by heating only one end. (Actually, that's not true. I would harden & temper the whole thing. Temper at 1-1.1 KF and the RC is only 47-51 with darn good impact resistance. And real good resistance to temper drawing.)