All right...since cadomax's map of this level doesn't even HAVE all the spots circled for where the spikes appear....SO....since I died, again, on this level, I'll post what I know about this level so far. All the circled parts are where spikes for sure show up from my own experience, and where you are supposed to leave the level. This whole level is one giant trap designed to lull you into a false sense of security.
Level 54.9 Spike Locations