First off, I would say get together with whoever is putting in your embryos (recep herd) and whatever makes everyone happy and is agreeable to by both parties would be acceptable. There are just too many variables to completely go through to adjust the value of everything.
That being said, I also am a firm believer of "if it is worth owning, it is worth owning 100% of it." If I truely believe an animal is worth $10,000, then I should be able to back it up by purchasing 100% of that animal. If I am looking for a partner it is because I want to "spread/share the risk". If I do not have that amount of money laying around when the opportunity arrives, then my banker should be willing to loan me the money "since the animal is worth $10,000". If not, then the animal may not be truely worth $10,000 or I have made my banker skeptical of my "business sense".
All or nothing for me! Give me all of the success or all of the failure. None of that "half of page of partners" for me!
My embryo recep herd has tons of experience putting in embryos, has the BEST management, and have proven themselves over and over. I pay a price over market and implant fee. Nothing else. Every single calf that results is mine, regardless of quality. In fact, this year he is changing his "price" to a bid off process, with the highest price getting their number of embryos in, then the second highest bid to get theirs in, then the third... etc.etc.