Yah, I saw where you talked about avoiding the stud ... hence the warning that there may be studs in the bathroom where there shouldn't be any (based on 16" centering).

I'm not trying to scare you away from the fasteners that you chose but that 800 lb rating is for the fastener installed under ideal conditions. I'm sure that it's a great product but the Engi-Nerd in me forces me to exercise caution X4 since they will be used for mounting a safety device.

The 800 lb rating is for mounting it through tile that has been properly glued to the wall ... & the wall is greenboard or better ... & the wallboard was installed with screws rather than nails ....

If you trust the construction quality of your house then those fasteners should be fine. Both showers that I've worked on in my house had regular old sheet-rock behind the tile (fine for modular showers ... not so much for tile).

The blue prints for your house may not be much help. They are basically assembly instructions for the builder. How many times has hubby assembled something using the instructions & it came out ZAKLY right? Blue prints are a good thing but not for locating studs - they just don't have the resolution for that (prolly don't even show the extra studs I mentioned in my earlier post).