1-1/4" thru I joist above bearing point
Each truss manufacturer have specific requirements for drilling holes in their joists. You’ll need to verify the JOIST TYPE (structural type based on flange size, species, etc.) and SPAN with the manufacturer and then determine where they allow holes. 

However, here is an installation guide 

https://www.bc.com/wp-content/uploads/2015/02/UK_Install_Guide_A2.pdf

from Boise-Cascade which I’m sure will be similar to most manufacturer’s installation instructions. If you notice in the upper left hand corner, holes are to be drilled in the center (the neutral axis) and size depends on distance from the support. 

These joists are specifically manufactured based on loads, spans, etc. and modifications to the joists should be done to the manufacturer’s instructions....random assumptions about drilling 1 1/4” holes just 1” from the bottom flange is not recommended.