Estimating opponent call ranges

I've just started $33s (hey Scuba) now that I got my BR up to 100 buyins. One thing I noticed right away is that my bubble play isn't nearly as good as I thought it was.

So I'm loading up my hands in SNGPT and realizing that a lot of the hands I'm having trouble with will swing depending on what the opponents call range is. Trouble is, I don't really know. Seems like the presets as eastbay generated them are generally tighter than what I've been experiencing, but I haven't played enough to be sure.

Can anybody out there (*cough* Raptor *cough*) help me figure out how to estimate my opponents call range? Is it just a matter of waiting and seeing what his poorest calling hand is? If you have no read, what do you assume? Is your assumption different between $33s and $22s?

Thanks!
Baz