So, I was doing some work in Flopzilla on the best way to defend vs. 4X raises from the Small Blind when it's been folded around, and I came across the following problem:

Let r = % of time we realize our equity 

If we set r = .85 and we also assume that the Small Blind opens 33.3%, then we must defends all hands with the following equity based on pot odds alone:

(3/8)/r = Equity Needed To Continue

(3/8)/.85 = .4411

So, pot odds tell us we should be calling all hands that have 44.11% equity or better against a fairly linear 33.3% opening range. 

Game theory, however tells us that we need to be defending 1 - (3.5/5) = 30% of hands.

Thus, if we 3-bet our strongest hands and balance with "bluffs" at a 2:1 ratio, we need ~16% of total hands at minimum to call.  

Running some equities against the SB Opening range in Equilab, though, I find that it's very difficult to find ~16% of total hands to call without taking a dip in either EV or playability. A hand like Q9o only has 41%.

Therefore, if we are going to play a raising range from the Small Blind vs. The Big Blind, is raising to 4X actually a pretty good play?