"Spoilers on airliners are not particularly effective, in fact sometimes I think they produce more vibration than drag. I refuse to accept there is ANY appreciable drag below 100kts, and very very minor drag up to 140kts."
Guess you're unfamiliar with the DC-9. . AeroMebbe crashed one after emergency descent, as it wouldn't fly with the spoilers still up. I was once SLF just aft of the wing on an MD-80 that was trying to hold at 6K feet after descent toward KLAX. We were getting pre-stall shake until he retracted spoilers. Yes, I've been on big airplane test flights, and know stalls. Ever watch the Horizontal stab of a DC-10 during stall? One of the techs said, "Oooh! Wish I'd never seen that."
In all this discussion, I have seen no mention of fuselage blanking lift on the downwind wing.
GB