Newbie cable and standoff question for shield product

Hi there, I recently purchased the Screw Terminal Breakout Board for Particle Photon and I had a couple of questions:

  1. What diameter are the PCB holes? I am hoping to buy some adhesive standoffs and I bought these designed for a 0.125" PCB hole, but they appear to be too small as it’s not a snug fit

  2. I am trying to connect the breakout board to this RS232 TLL adapter which can accept female jumpers. I’ve got some 26 AWG female jumpers and when I strip one end to screw into the terminal block, the exposed stranded end seems pretty flimsy and makes me doubt its reliability in the long term. Will this be fine / is this just how it is, or is there a better / more hardy approach?

Thank you!

1.The holes diameters is around 4.6mm.
2. female to mail jumper pins like this one