ROI for 180 person SNG's

[ActionDavidK]

I have done pretty well in regular mtts in my short career of about 400 mtts. I have an ROI somewhere around 120% to 150% playing mtts with buyins from $3 to $30. At the beginning of this week I thought I should give the 180 person sngs on stars a try bc if I can have the same ROI I could probably play more of them. I'm playing a combination of $4.40's and $22's. Over about 120 sit and go's I average an $11.80 buyin. This is about what I expected. What bothers me is that my ROI is a lot lower than I thought it would be after 120 sit and go's. It's at 31.7%. I relize I'm one first place, in a $22, away from having over 100% ROI. For those of you that have played a lot of these sit and go's, what kind of ROI should I expect to get and how do you approach the end game? I feel like I should play pretty aggressively during the end game, more aggressive than my mtt style, bc the payouts are so top heavy.