Great, then I would put them all in 1 questionnaire. Assign all the items of each treatment the same BGR value. This will randomize the order of the treatments while maintaining the order of the items within treatments. After the first 5 treatments, insert a simple Instruction item that has a skipto value of "end" or perhaps a debriefing screen you have as the last item in your session. Give it a BGR value of 0 as well as that final item. That will do it.

The idea is that all the treatments will be randomly ordered, but the experiment will skip to the end after the first 5. Voilà! See unconditional skipping in the randomization sections of the user guide for more detail.

Hope that helps,
Blair