No at all, a splice guarntees 90 to 100% of the breaking load. The breaking load reduction of a knot depends on the rope material. For Dyneema it is said to be around 80% reduction, hence 20% of your breaking load are still usable.

If you have a 500kg breaking load trap line, you can still use 100kg on it, which should be sufficient.

Dyneema creeps about 5%, but if you pre stretch the rope (e.g. with the main sheet) you can solve this problem. After this 5%, I didn't notice any creep on the trap lines. Some suppliers deliver pre stretched ropes as well.

Cheers,

Klaus