It turns out that the
wrist rest I added, which extends the entire length of the keyboard tray on my desk, makes it uncomfortable to use the mouse.
To re-elevate the mouse I made this thick mousepad that I'd rather call a "mouse elevator."
The polypropylene is translucent enough to allow for occasional artwork/photo festivity :playball:
I assume it doesn't work for an optical mouse but it works fine for my laser mouse; it now sits ½" higher, which is just short of the wrist rest, but it's all good.
Effectively, the keyboard is now sunk in the tray, after I either adjust my chair upwards, or quit slouching as much.