[Freesurfer] optseq and psychometric function

Dear List:

I have a question concerning optimizing the presentation of a psycho- metric SCASE procedure with optseq. Subjects will view two interleaved SCASE in the scanner. SCASE1 and SCASE2 test the whole length of stimuli strengths for two different conditions. To obtain the best sequences in optseq do I register SCASE1 and SCASE2 as two conditions, or should the individual test steps (ie at 10, 20, 30 % ...) be listed individually as conditions ?

Does registering only SCASE1 or SCASE2 without breaking down into individual test units provide accurate efficiency and cost functions in optseq ?

Finally, is an efficiency of 25 good for such a design ?

Thank you very much for your help!