Print with Raft, No Support (as it's designed in), 3 shells / 4 Shells for 5th Generation Replicators and 35% fill. The rear is designed to stay hollow so it will stand on its own 8 legs without falling back. The designed in support should break away relatively easily but take care with the legs as, like real spiders, they are thin and can break easily (...these are far stronger than a real spiders legs!).
Note: Reducing size is not recommended as it will weaken the legs and make the designed in support harder to remove... upscale as big as you like.