I'm designing a CBC Experiment with 4 attributes, each with a different number of levels (5, 3, 2, and 3 respectively). This will be a paper and pencil survey and I'm anticipating about 60 respondents. I'm considering having 4 concepts per task, along with a "none" option. I'm interested primarily in main effects, but I don't want to discount interactions either. I have several questions that perhaps there is no easy answer for.

1. Is 8 an appropriate number of unique versions?

2. Should I use a balanced overlap, complete enumeration or entirely random design?

3. Would the design I use change the optimal number of respondents?

4. In regards to Question 3 I've read this post https://www.sawtoothsoftware.com/forum/8399/sample-size-cbc?show=8399#q8399. I was wondering if there is another way internally determine what is an optimal sample size.

5. Is having 12 tasks sufficient, given an anticipated 60 respondents.

I'm testing design efficiency at the moment, but I hope that by finding answers to these questions I can save some time from avoiding a trial and error way of finding the best design.

Thanks very much!