They could probably fill one, PMI is a popular destination and I know a number of people who live on the same road as me who often holiday there. Like I said they managed good loads with an A320 so I don't think filling a 757 would be too much trouble at least during the peak season anyway.
The 757's weren't' that restricted, they could just about make TFS with about 4 or 5 rows blocked off and the addition of winglets since then should enable the 757's to operate more profitably.