Hey del, I have the c serpent v70 racks and what Chris told me was to not place the probe inside the tub bc you will burn out the heat tape !!! When using a rack system I don't think you need to worry about a "hot" spot like a vision tank. Racks are different and they usually are back heat or belly heat models. The belly heat is recessed and I really don't think a hot spot is called for in the rack system. The other thing is to make sure you don't have the tape over the probe bc that will give you inaccurate readings to the tstat. Tape the probe wire to the heat tape but absolutely don't cover the probe with tape. Good luck.
Actually, tape the wire to the surrounding structure of the rack but let the probe extend over the heat tape. That way the probe is not covered or restricted.