you can't splice qpowerline because it's cored, but you can knot it (you can't knot 12 strand line but you can splice it). So on the non-flag out line it's possible to replace it with q-powerline and figure 8 a knot behind the plastic Y, but on the other end, it needs to feed through the line, so if you put a knot anywhere it will catch and cause your safety to fail. You shouldn't take q-powerline and knot it behind the Y on the safety line, because when that knot runs through the rest of your safety system it will catch on the bar or some other place and fail when you least want it to. What you can do is get some 12-strand dyneema/spectra with poly coating, it's a bit thicker, 1.75mm or a bit thicker instead of 1.5mm and then splice where needed and replace your old lines.

Alternatively you can replace both lines with q-powerline and knot both behind the Y but take out that flag out system and instead leash on the depower rope if you have below the bar depower, or suicide, or possibly on an oh shit ring.

If you tie knots in spliced lines they will break the first time you put much pressure on them, I have seen it happen many times, don't do it.

you can't splice qpowerline because it's cored, but you can knot it (you can't knot 12 strand line but you can splice it). So on the non-flag out line it's possible to replace it with q-powerline and figure 8 a knot behind the plastic Y, but on the other end, it needs to feed through the line, so if you put a knot anywhere it will catch and cause your safety to fail. You shouldn't take q-powerline and knot it behind the Y on the safety line, because when that knot runs through the rest of your safety system it will catch on the bar or some other place and fail when you least want it to. What you can do is get some 12-strand dyneema/spectra with poly coating, it's a bit thicker, 1.75mm or a bit thicker instead of 1.5mm and then splice where needed and replace your old lines.

Alternatively you can replace both lines with q-powerline and knot both behind the Y but take out that flag out system and instead leash on the depower rope if you have below the bar depower, or suicide, or possibly on an oh shit ring.

If you tie knots in spliced lines they will break the first time you put much pressure on them, I have seen it happen many times, don't do it.

You can in fact sew qpower with a reasonable machine. Fold the line to make the desired loop. Wrap 10cm of the line below the loop with a narrow strip of kite repair tape. Sew a zigzag along the tape just like for sleeved lines.