What do you mean by there is a lot of room for improvement? Obviously I have a bazillion leaks - is this what you meant?
Suppose you had a bet with someone about the ROI you could achieve over your next 100 SNGs. You get $100 times the difference between your ROI and your opponent's ROI. Would you do things differently from how you play now? I would.
In the prop bet, I wouldn't multitable, or not nearly as much. I would pay close attention to timing tells and chat tells. I would watch how the players act on other tables they might be playing--usually if a player is involved in a hand he will tighten up on other tables before the push/fold stage. I would use a much more extensive HUD. (I would also make some spite calls against my opponent in case we played each other.)
I think there are many decisions where we are used to taking shortcuts that work ok, but which are not optimal. If you only play one table, you might be able to consider different raise sizes or bet sizes, and more carefully put your opponents on ranges.
I think most players have significant error rates. In backgammon, there are objective programs which quickly tell you that play A wins 0.060 points less than play B. Expert backgammon players might only make the right move 80-90% of the time, and estimate their error rates in millipoints per move. I think poker players also make many mistakes, but it is much harder to get the objective feedback. I think it is quite possible for winning SNG players to average giving up over 10% of a buy-in per tournament from bad push/fold decisions. This represents the possible improvement you can make to your ROI.