OK, take your brown dot and move it to the first straight panel (~ 1' off the upright) and up to be ~ 22 1/2" down from the top (it'd be better to measure down from the top of your panel to the center of your existing return and place the new one at ~ that depth).
Then, as we talked about before, lower the water ~6" below the bottom of the proposed return, At this point, you can remove the liner from it's track and pull it far enough out to drill your pilot hole for the hole saw (remember to have something between the wall and liner to FULLY catch the drilled debris!)
Use the outer edge of your new fitting to be a template for the cutting of the wall foam. (if you go too small, you'll have issues, if you go a little larger - it's not a problem
)
It's usually a 3" hole saw you need to install a new return fitting, but measure the one you will be installing and use the correct sized hole saw! You want to use the smallest hole saw, so that the hole is just big enough to accept the
outer diameter of what you'll be shoving through the wall without it scraping the plastic. Use a file to smooth the cut edges, again - keeping the filings from falling behind the liner.
For your plastic sided pool, you should be able to use a Hayward SP 1408 or SP 1411 inlet/ outlet fitting, if it's on a flat wall. Using one of these takes the wall foam out of the question - the seal doesn't depend upon the inlet/outlet body being flush to the wall. I prefer the 1408 because it only has 1 gasket. Going with the IG fittings I just gave you, you can, after the hole is cut and the unit installed, you simply install the fitting, put the liner back into it's track and refill the pool before having to install the faceplate and cut the liner
If you go with a standard AG fitting, and you may have to, don't be afraid to cut the foam out a little larger than the flange on the fitting, you surely don't want a little flap of wallfoam to keep the gaskets from fully sealing!
Again, I'm sorry for not being able to complete this yesterday
:-D 
