From our ebook:

Sparse MaxDiff / Random question allocation

The simplest and often best strategy is to create a large design and then randomly allocate

respondents to different questions. For example, if a design has 20 questions, each respondent may

be randomly allocated ten.

While this is a simple strategy, it is also a good strategy in that it is both simple and tends to produce

good quality designs.

Add an option to the design that will do the random allocation for each respondent.