Why do you have to play more hands in the early stage in a SH SNG? I don't get it. You shouldn't be forced to play more hands in the early stages just because it's shorthanded. Therefore you don't have to deal with more postflop situations, not more than if you had played FR SNGs.
Inherently, you should be playing more hands in shorter handed games. For one thing, the blinds are coming around faster, which gives us more incentive to be trying to pick up pots, even early in a SNG. Secondly, less hands are being dealt; there are less people at the table, and therefore, in its essence, you're simply at a 9 handed with 4 less people. So, if you're UTG in a 5 handed game it's effectively as if you were in MP3 at a full table and a few people had already folded to you.
Finally, people tend to play worse in shorter handed games. With playing more pots comes the tendency to divulge one's post flop leaks more, simply because you're getting involved more and playing more marginal hands with money behind.
So, to try and help further with your specific question, moldovan, it's pretty tough to assign a stringent preflop range for yourself in 5 max games. I'd say the more comfortable you feel post flop with your continued studies, the more you can be opening up your game early. To improve on it, I suggest keeping with the videos,and making sure to post hands for discussion. Finding a study partner is important to, as having a person(s) to ask random hand questions to and to sit down with and collaborate is just so crucial for one's development, even if via email once a week or something. It also might not be a bad idea to watch some MTT and cash game stuff. There tends to be more post flop discussion in these due to the deeper structures and more room to play; the more you hear good players talk about post flop play, the more likely you are to pick up a thing or two about improving your thought processes. As long as you're making sure that you realize that you're applying this to shorthanded STTs and not the cash game or MTT or w/e. Always going to be differences, but they can still help to a certain extend IMO.
In the end, though, putting in the volume and constantly reviewing your own play and discussing your play with others is going to be the key to most peoples' improvement.
I wouldn't adhere to this strictly, but some things that I personally do differently in 6 max SNGs as far as early game preflop open raising ranges that I am tighter with in FRSNGs are probably as follows:
-Raise more pocket pairs (personally I raise 22 utg in a 6 max with 5 other randoms but there are arguments for folding and limping still, too).
-Opening more Ax hands; UTG AJ and ATs do become opens where they often aren't early on UTG in full ring games. From later position you can definitely go wider than this, too. I'm not folding any Ax hands on the button. I'm not open folding KQ pf generally ever.
-Isolating limpers wider- A lot of the time, when you see loose limpers in shorthanded games they probably just are not good. This can go for full ring also, but limping is often more correct in full ring contexts. The more limping preflop you see in shorthanded games, the worse they are likely to be. I'd be isolating loose limpers with all sorts of attractive looking broadway hands, often pairs, and perhaps more marginal Axs hands or high connecting hands, but the more of a read or feel for the table context I have the wider I'll go to this extent.
Those are probably the big areas to look into. I haven't played 5 max specifically, so the payout structures are very important to look into for ICM considerations and they might differ from said implications in the 6 max setting, but the early game is probably going to be similar.
Post some hands in the forum and I'll try and take a look if I see them. Good luck.