The most important thing is to come up with a method that is agreeable to both parties and put it in writing before the pairings. That will eliminate any misunderstandings and hurt feelings. If you think there is going to be the possibility of an interesting morph produced, you need to address that in your written agreement.

Having a written agreement clears the air and sets the proper expectations. The agreement can be a simple handwritten document that both agree to. Make sure each of you have a copy.

Good luck.