I had this happen with a Monic line. Their clear freshwater lines are SUPER soft. I have used several methods, all of which worked well.
I'm a big fan of Cortland leader loops, but if that's not your cup of tea, most folks here seem to like Amnesia for this kind of thing.
When I did one of mine, I used 20# fluorocarbon, so I can't imagine the 17# being too thin, although that is a distinct possibility. One thing I also did was hit the end of the line with a Zippo to kinda seal and weld it before I added my fluoro loop. But that would probably only work with a line with a mono core.
I have also used the recommended method here, minus the acetone. I cut off the outer coating with a box knife:
Loop connections - Loop on a fly line - Global FlyFisher
If, by chance, this is a Monic line, their core looks to be plain monofilament. It's a little slick for that method, so I used a good bit of glue when making it.