Mutt: re DC-8's... yessir, inboards are used to drop out of the skies for emerg. descent (but NOT used for ducking back to the glide when turned onto finals too early!!).
BN2A: You are bang on about using idle reverse only when one is locked out... of course many of us have been guilty of briefing "Idle reverse only on the good one" then after a long duty-day / long block of min rests...we still slam them into full reverse with a "AHHH CR@P!" then correct ourselves by zipping it back to idle with nothing harmed but our foreheads from smacking one's self for the boo-boo...
Cheers,
Ray Darr