Originally Posted by
randyjawa
Undo the wheel install guide, to remove the screw from the brake plate. Slide the pad in and replace the screw. Pretty much as simple as that.
THIS. Beat me to it.
Originally Posted by
pfreyre
Thank you all so much for the advice! I ended up using a razor to cut a groove from the end of the pad to the hole in the middle. It seemed like the only way to make it work - what a stupid PITA design! I’m sure that higher-end Modolo, and Campagnolo brakes had a much better-engineered design than this.

Don't try to hold yourself in place with the brakes at a steep uphill stop. Because the pads will slide out backwards. The retaining hole (was) there for a reason.