I'm playing a small site and during some hours the traffic can suddenly drop really low at some stakes even during peak hours.

I'm afraid to play across several stakes because all I know is that it increases the variance.. would suck to win nice hand at the lower stakes and then get a cooler at the higher stakes. 

Is it possible to mathematically answer this with some formula? 

Because I remember reading an article about SnG's + MTT's where a person mathematically showed how the variance changes when you play several stakes, mixing MTT's + SnG's and how you need to play for example 2x $50 MTT's for every $100.. if you play 2x $50 + 1x $100 then you can play a $200 MTT as well.. and so on.. It's high variance though and no fun to play and win a bunch of SnG's so you can play a MTT that you lose.

Is there something like this for cash?