If there is a limper in front of you do you still raise 3BB as an open? Same applies to squeezing - you should raise the size of your 3bet when there are extra callers as standard; this helps you get the maximum out of your value hands. I don't think that terms like 5x or 4x are of much use when it comes to 3betting. I believe it is more useful to think about your bet sizing in terms of what odds
you are giving your opponents to call. A raise to $1.15 would make the pot $1.80, your opponents now have to call $0.90. This is giving your opponents 2:1 which is a reasonable 3bet.
So lets say instead we raise to $0.75 or "3x". This makes the pot $1.40. Your opponents would call with pretty much there entire opening range getting a ridiculously sick price so what's the point making the raise in the first place? This is why I advocate making the raise slightly larger. Additionally, you said about reducing the SPR: actually if you think about it, if you raise $.75 and get two callers you have a pot of $2.40 going into the flop; raise $1.15 and get one caller and you have $2.70 going to the flop, so you're against a single opponent in a very slightly bigger pot. Sure you could get everyone to fold but this isn't the worst since you only hit the flop around 1/3 of the time, but by raising more and thinning the field you have a greater chance to steal the pot post-flop if you do happen to miss.
EDIT: made a few more points