Robotic Pyeloplasty and Endoscopic Stone retrieval

I was recently faced with a case of a right sided UPJ stenosis with good renal preservation and two 5 mm stones in the upper pole. Having done at least a half dozen robotic pyeloplasties I felt that that would be the appropriate treatment for the UPJ but was not sure how to address the stones. I did not want to leave them in place and have to address them later. A separate percutaneous nephrostolithotomy seemed like overkill for the size of the stones. A PNL could be combined with an antegrade endopyelotomy, but the stones were in upper pole calyces and the combined procedure might require two separate entry points for adequate access (lower pole entry point to reach the upper-pole and a mid- or upper-pole entry point to reach the UPJ).

I am at a point in my career that has not afforded the experience of younger surgeons in laparoscopy so some of this I have to make up as I go along. I placed the three ports in the standard fashion for a pyeloplasty (we have only a 3-arm, not 4-arm, system). I had a 10mm port above the umbilicus on the midline for the assistant and during the case we placed a 5mm below the umbilicus and to the right of the midline. Once the renal pelvis was open and the stenotic portion excised I held the kidney in position with the two working arms and stepped away from the console. The arms, of course, locked into position. I then passed a flexible cystoscope through the 5mm port and, using the image on the da Vinci room monitor directed the tip into the open pelvis. At that point I visualized the two stones with the scope’s optics and, using a zero tip Nitinol basket, extracted the two stones in sequence from the upper pole calyces. They just fit through the port. I could have used the 10mm port for a larger stone but the placement of the 5mm port provided a direct shot at the upper pole. A ureteroscope could, of course, been substituted for the cystoscope but the anatomy did not appear to require it.
I then returned to the console and completed the anastomosis.
Several thoughts come to mind:
1) How large a stone would one be willing to approach in this manner?
2) If a stone or fragment were to go astray in the retroperitoneum or peritoneum and could not be located, what, if any, are the consequences?
3) Would anyone consider this approach a replacement for PNL for treatment of some larger stone burdens?