The posts are too close together, I'd have to unmount everything and extend the rack, huge pain. Even if I did that, the rails were designed to interlock with the front of the server, which would be blocked by the other half of the post, so they wouldn't slide all the way in.
First of all, great to have this information so that others know what to look for and solve the issue.
So a big thank you for both the images and the solution.
I too have the startech 4post rack. And yes, the C shaped post do get in the way sometimes.
Mine is fully extended so the length of the rails would not be a problem for me.
I don't have a SM chassis yet but might end up with one in the next few months. HP, Norco chassis and other parts for now.
I don't know what you mean with "designed to interlock with the front of the server".
Do the chassis need to reach some part of the rails in order to stay put in the rack?
What's the downside of the chassis not sliding all the way in on the rails?
If you mean that the chassis has screws to hold it in place to the post/rails you could allways use a cage nut on the front post for that?
(I do that with my IBM KMM)
Do you have the part number for the rails you returned so I can check the PDF for alternative mounting options?
From the pictures I like the new rails better then the old ones so was hoping that they fit the startech 4postrack too.