Partnership guaranteed payments or payroll for 401k contributions?

A husband-wife partnership has adopted a Solo K. It will receive management fees for providing management services to other real estate holding companies the husband and wife have. Can the partners receive guaranteed income payments and use that amount as contributions into the Solo K—or are they required to run it through as payroll and spit out W2s for each spouse? Trying to keep things simple on the 1065 and avoid the expense of running payroll. 

Happy Fourth! Go Team USA!!