So 60 ft should work. The AC of a normal mirror should be 3, I guess, since it's Medium-sized.
Sure, AC 3 is what the rules say. The original scenario gave the mirrors AC 5, which is AC 15 in 3E, so I suppose we could give it some NA or something.
Oh, and how many hit points are we giving them? They had 20 apiece in the AD&D adventure, but our placeholder uses the 1 hp of an inch of glass.
Hmm, come to think of it, what are the mirrors made of? It just describes them as being "rose tinted". In real-life ancient Japan the mirrors were polished metal, but the adventure says they "do not crack, but shatter when destroyed", which sounds more like glass.. Still, we could give them respectable hit points if we wanted to.
He looks about CR 11 to me, maybe CR 12. What do you think?
I was thinking a little lower than that, maybe Challenge Rating 10, since it's not
that much nastier than the CR 8 Reaper and Veiled Maidens. It certainly doesn't feel like the +4 CR difference that CR 12 would require.
The General's got 4 HD more than the Reaper, which'd be +2 CR if they were dragon/outsider/nonassociated class levels, which seems about right.