Without reference to the big picture, an immediate implant (7x17 mm gingiva-level) for #2 tends to be placed with mesial inclination; sinus lift (sinus floor: red dashed line) will be uneven with tendency of sinus membrane perforation (Fig.4).  This is a sagittal section of CT, which was taken 2 years earlier when bone loss around the tooth #2 was not severe.

Even Sinus Lift

Xin Wei, DDS, PhD, MS 1st edition 01/11/2015, last revision 01/11/2015