Running backs -- continuous line or two part?

[memelet]

I was planning in using something t900 (partially stripped) or amsteel (partially covered) as a single line to my winches . I also want to setup the shock cord retractors described in a earlier post.

But today one of the riggers at the yard where I'm doing my work admonished me against using a single line. He said I should amsteel with thimble connected to the tail. His reasoning was that if the uncovered line gets damaged on that part would need to be replaced.

Sounds reasonable and I would no problems doing that, but I'm concerned that the thimble will interfere with the retractor block at the end of the shock cord.

First is it so important to use two parts?

And second, if I did use two parts, I'm assuming that the retrator block would need to below the amsteel on the second covered part. But in my mind (I'll probably draw this out and do the geometry) the block will want to roll over the thimble with this setup.

Can someone set me straight? Thanks!