acceleration at high tempreature conditions

Yes, Steve. At 973K my box is nearly 3 times bigger than it at 300K. So under this circumstance , is there any possibility to accelerate?
My test results are shown as follow,

> speed (percentage)
1. default
2. ksapce_modify diff ad
3. -sf opt
4. kspace_modify diff ad + -sf opt

So maybe kspace_modify diff ad is my acceleration choice.
BTW, what are your suggestions?
Thanks in advance.