Mud-flaps

[librarian]

Normally, slacken the 4x nuts on the stays, wiggle the mudguards out a bit then retighten.

Adjust the mudguard indeed!

JohnP's low-tech approach is a bit disappointing, frankly.

Get a smaller rear wheel, tube and tyre. You may need to change/replace the gearing (and possibly entire drivetrain). Consider whether deep drop brakes will be necessary, or (if fitted) having the canti bosses moved (professionally, of course - necessitating a respray).

There, sorted!