The few times I have come across this joint I also use 3-8-1 lap Joint. Then I explode the cutout on the purlin and then edit the "Length Position X" & "Length L" on the same cutout to the desired size. You can then use 3-8-4 Notch on the rafter to create the housing.
If you had a lot of these joints a customized smart tag would be very useful!
