Syntactically it is valid, but it is not going to avoid dominated alternatives and other things you wanted. Designing a realistic choice study is not strictly about maximizing design efficiency. We can never actually even know what efficiency is. All we can do is assume a beta vector, typically zero, and go from there. More important is ensuring the design is realistic--no dominated or unrealistic choice sets--and further ensure that all parameters that make sense can be estimated with some realistic degree of precision. Hence the recommendation to use the ChoicEff macro to evaluate the final design. These topics are discussed in great detail here.  https://support.sas.com/techsup/technote/mr2010c.pdf I know it can be a bit technical at times, but I tried really hard to spell out everything I have ever known on this topic in this piece. Best of luck in your research! ... View more