Suited connectors are actually pretty bad hands to be calling 3 bets in short stack situations of heads up sng's.  If you think your opponent is 3 betting you "tight" then calling with an SC trying to spike a big hand doesn't leave you with enough implied odds.  If you think your opponent is 3 betting you "light" then it's much better to call with big card hands which hit good made hands and bluffing situations like overs+gutter.  Another option is to shove over his 3 bets as a semi bluff but you want to have a feel for how often he 3 bet folds vs calls.

The value of low and mid suited connectors goes down in HU, having said that though it depends on the opponent, but against most you don't want to be calling 3 bets with them.  Situations where you might consider calling is against an opponent who plays fit or fold and will check fold most flops, or if you get min c-bet and it only costs you a little to call, where you're getting odds to all with any 2. 

if you want to see the value of SC's, open stove and fuck around. I dont do it too often because most people dont 3b light at my stakes but when playing higher and vs better/ more aggro opponents, I will 4b shove with sc's here and there. Want to know why? Use stove and findout

The value of a suited connector goes down when the effective stacks go down.This means that most of your calling of 3bets with suited connectors will be occurring deeper stacked, 50-75bbs deep.They are hands you can get into a lot of trouble playing, so usually fold them unless your opponent is exploitable enough postflop to where you can steal a lot of pots or the size of their 3bet is much smaller than average, 2x or a min 3bet, for example.

Even with large effective stacks you do need to make sure that you'll get paid off if you hit a big hand with these, you need either an aggro monkey or a station to make sense of it.  You can 4 bet shove them if you have enough fold equity but you need to be careful doing this and you need a good read.  The lighter they 3 bet and the more they fold to 4 bets is what you want of course, and you need both really, plus large effective stacks to not have the guy committed to calling.  Against most people I'd just throw these away when you get 3 bet, things have to be clearly going your way to do it, you won't have a good draw most of the time and there will be at least one high card on the board, he c-bets, that's just a tough spot you don't want to get into too much.

"Even with large effective stacks you do need to make sure that you'll get paid off if you hit a big hand with these, you need either an aggro monkey or a station to make sense of it. "On the other hand, if the opponent is weak/tight, you can have enough fold equity to call with these hands profitably, not to mention when you BOTH hit your hand you will get paid a high % of the time, as your hand is more disguised with a suited connector when you flop a monster.Good points all around though.

Yeah sorry I had that in an earlier post, the fit or fold players that will check fold most flops, however this will allow you to play more hands in general against them, and when they do call you then you've got a better chance of hitting top pair when you're playing for high card value.  Now this does allow you to make bigger hands as you say but these players will often be wary of boards too wet and given the odds of you hitting it combined with their odds of having enough of a hand to get a lot of chips in, that's pretty slim :)  In general a lot of players tend to overestimate implied odds, geez if I hit my hand I can get his stack but he's not stacking off with less than 2 pair we'll say so you can't really use the kind of numbers that people tend to do.