I think you will need a power tool to pull them.
One thing I didnt mention - probably obvious - is to be very, very careful to deburr the holes both sides.
The probelm is that the rivnut relies on its crush generated clamping force to resist torsion. Thats exactly what happens as you tighten the bolt up. The stronger the bolt to rivnut meshing the bigger the problem unles you use torque wrenches every time.
What happens is that the rivnuts will gall on the softest material and then rotate. If the bolt gets corroded a bit in the rivnut hole duriing service you rotate the rivnut and cant ever get the bolt out if its into a blind space because there is nothing to grip on.
Guess exactly what I did !!
Get a bolt/setscrew plus a loose nut and washer. Screw the bolt - full thread depth - into the rivnut, run the nut down and push the washer against the rivnut. Hold bolt stationary with a spanner, screw nut down with another spanner. This sets the rivnut. Don't just pull up the rivnut by turning the bolt - result is stripped threads & much cursing. Experiment a few times. Add Loctite/sealant to taste.
Also follow all Mariner's advice.