I used spectra cord with tracers for my most recent pack build. I haven't gotten to use it, as I finished it yesterday, but I cannot see any problems with using it. It is very strong.
It looks like you tied the two d-rings together with spectra in your picture. If that is the case, you may want to use a taut-line hitch. That way you can adjust the compression. Slipping could be a problem, but it would also be better than having to tie a new knot each time I would suspect.