Bubble calling ranges in $11s and $22s

[The Deuce]

I've been tinkering around with SNGPT a lot lately in an effort to sharpen my game on the bubble and 5 handed before I move up to the $22s, which should be within the next few weeks. The problem that I keep running into is in assigning call ranges to my opponents. I often find reads from earlier levels unreliable once the blinds start getting large- for example, a guy that's been playing tight the whole tourney all of a sudden decides that he's going to the felt with K4 on the bubble when I push from UTG. Basically my question is, when evaluating whether a push is +EV or not at these stakes, what default calling range do you generally assign to average opponents, barring a really strong read? My tendency is to fall back on the L range, but switch it to an M and all of a sudden pushing that 76o from the button is a disaster. I've had decent results so far, 19% ROI over about a thousand tourneys, but I still often feel like I'm fumbling around in the dark in these situations. Any insight from more experienced posters is much appreciated.