If the fish line was wrapped around the post without any space between it and the post, the tendrils would be unable to wrap around the fish line.

If this were mine I would attach a ground level (6 inches above; using L brackets), 2 horizontal pieces like what is near the top (or 1 long piece). If the top horizontals are at 12 o'clock and 6, the lower pieces would be at 3 o'clock and 9. Then I would string the fish line up and down between these horiz. pieces. The biggest problem will be making knots that hold in fish line. Polish Spirit is vigorous after getting established and needs severe yearly pruning. The fish line may come awry with removal of last year's growth and need replacing.

Fishing line is slippery and perhaps a bit more difficult to hang on to so the weight of the plant may make it slide down. As irisgal said, fishing line may come away with the vines when you hard prune, and if you compost separating them may be difficult. Would you consider using twine that can be composted with the vines and will offer a more grippable surface? I would probably run twine from the crossbars down to pins at ground level since that will give your vine plenty of room to grow.

Since you only planted your clematis last year, it may have already begun its growing in a certain direction, so it may not be as much of an issue this year as far as needing encouragement to grow up the strings. If you haven't pruned it down to 1 or 2 sets of buds, do that now before it puts out leaves. It will grow back fuller and will quickly reach last year's size and continue growing. Since PS blooms on new vines, pruning will also help the vine flower from bottom to top rather than just at the top.

You can also use wire grid fencing in a circle around the post or I have seen half circle trellises on Amazon that you could buy two of that look nicer. In my experience, Polish Spirit is a monster and will swamp that post after maturity even after pruning to the ground annually. I have it trained up a crabapple tree and it has swamped the surrounding shrubs and perennials and killed them all as well as going up into the tree. It seems to grow as wide as tall. There must be a hundred stems/vines up from the ground....from a one gal sized pot a few years ago.

Thank you so much. I'm testing twine this year based on feedback. I did one string straight down from each cross bar. Not sure if I need additional strings or if two will be adequate. Guess we'll see

I'd give it at least 2 and perhaps 4 from each crossbar. AS BorS888 commented, this is a quite vigorous clematis, and 2 won't begin to accommodate the vines.