A word of advice: if you're able to get to the gate early (gate agents usually get there at T-65 minutes before departure but I would aim to be standing and waiting at the podium at T-70 at the latest) and "claim" those seats I would recommend you do so (especially 10C).
I'm
#1 on the C+ upgrade list a lot on 739s, but my upgrade success rate into 10C is probably only about 10% when I'm
#1 on the C+ list on a 739 (which means I end up stuck back in Y) despite the intuition that the upgrade should clear most of the time. I have a pretty good sample size too (at least 20-30 instances in the past year) so this is not a fluke or anything.
While obviously there are occasionally pax with disabilities, the majority of the time this is not the case. Gate agents seem very amenable to either:
1) People already in C+ asking to be moved to an aisle (when they have a middle seat)
2) Cranky non-statused pax trying to sit next to someone when they are split (or any variation of the "but I need an aisle!" spiel)
The end result is that often times there are no window/aisle C+ seats left by the time C+ upgrades clear - meaning I stay at
#1 and no one clears (even if I select all seats, gate agents generally don't clear people into C+ middle seats unless you specifically ask).
I spend a
lot of time in 36C on 739s... good luck!