outs for draws

[ccwhoelse?]

if you are on a draw and if you are sure the other only player in the the same kind of draw is it ok to reduce your number of outs to compensate for this, as he might hold a card or two you need for your straight while you hold a card or two he needs.

isn't it also reasonable to assume, in a 10-handed game that your outs on a four flush aren't realistically 9, even though you have only seen 4(your two plus the two on the flop).

thanks.