What is the maximum allowable memory for the Mac Mini (mid-2011)?

2 x 8 = 16 GB.

Just to add, make sure you get RAM from reliable sources

as Apple products are a bit finicky as far as RAM.

Around here, OWC and Crucial seem to be the most reliable options.

Personally in the past, the "Mac Branded" RAM from Corsair and

Kingston have worked well for me. Avoid any "bargain basement"

PC RAM or any RAM that just says "Mac Compatible". I've been

there, done that, been burned (it was PNY in my case).

You’re welcome!