Recurring Task

I have a master project consisting of linked projects to the resource pool. I have a recurring task and it

1. ocurrs every monday till end of the year
2. lasts 1/2 day so have set the duration as 0.5day in the recurring task information box.

when i assign resources say Bob and Jim do i:

1. Change the duration to 1 day in the task information box
2. set the activity as fixed work
3. Put the "unit" as 50%.

The reason why i ask is because when i set the activity up to have a 0.5 day duration, change the tasks to fixed work and add a resource and allocate 100% in the unit column, it makes that person 100% for that day rather than making them 50% allocated

Thanks,
G