I ended up doing something a bit differently. I have ordered a set of C5 bearings from a company in China. I asked the sales person point blank about my concerns with preload between the two bearings on the fixed end and he was able to satisfy me with his answers. I bought them direct from the manufacturer. He says they are true C5 quality and better than the SYK C7 and PVP C7 I was looking at. He said they were closer to misumi in quality than those, and the pictures on the website looked great, so I purchased 4 FK15, and BF15's, and 4 extra nuts (I've heard it's better to use double nuts, what do you guys think?). I'll have the ends of my ballscrews machined accordingly, I will need custom lengths regardless, and the end machining is included in the cost of the ballscrews. Here is the pic he sent before shipping:
Attachment 360152
I hope I made the correct choice. I will let you guys know what they are like when they arrive. I expect shipping to take a month.
I'm also ordering a set of 4 SYK MBA 15-F motor brackets from a different supplier. I'll let you know how that turns out as well.