Last night I lectured on the Cross over gait. I discussed at one point using one sided carries, a heavy farmer's carry, to stimulate more activity on the stance leg , particularly focusing on driving more hip stability. But, it matters how you do it.
The photos i have attached are both technically a farmers carry unilaterally. One I am working my gluteus medius and hip stabilizers more, and the other i am using my lateral abdominal chain more (more of a compensated Trendeleberg type gait, and we know that hip pain patients lean in a Trendeleberg gait to reduce the activity of the glute medius to reduce compression across the joint (2/3 reduction)). If you are trying to help your client reduce their cross over gait with more hip stability building, one of them is going to hit the mark far better than the other.
So, if your clients are walking a line in their Farmer's carry, think about what you/they are actually doing (likely less hip stability stimulation).
The exercise should fit your goal. Have them walk feet on either side of a wider balance beam to get more stance phase glute activity (try it yourself, the wider your step width the more hip loading you get), or, have them walk a line and lean more into the frontal plane to get more abdominal. It is not a perfect science, but you do get a different feel from how you do it.
But, it matters how you do it.