That's no excuse to make it ugly. There are plenty of ways to achieve this without massively cluttering it.

Just look at Canada, Australia, or even Mexican plastic currency. These are nowhere near as bad but are just as secure.

Canada: https://upload.wikimedia.org/wikipedia/en/9/92/Canadian_Fron...

Aus: https://i.pinimg.com/originals/d3/91/b8/d391b8dafd8c60277a81...

MX: https://www.inside-mexico.com/wp-content/uploads/2015/08/Fot...

Truth! There's always a human element though... A previous employee of mine once accepted a $10 bill that turned out to be a $1 bill with a zero drawn in black marker on each corner of the bill by the ones. The store was insanely busy that day so I can kind of understand how she let it slip past her, but good grief.