I had the same questions wrt my RS-50. Page 21 of the installation manual has a couple of charts describing acceptable combinations of vertical and horizontal lens shift. It's a bit of a head-scratcher, as they refer to a % of the image height and width. In my case, with a 52" H screen, the 80% point is 41.6". Subtracting that from 52", I get a maximumm drop of 11.4" from the center of the lens to the top of the screen. That's a number I understand from my CRT days.
For your install, calculate the % of vertical shift you'll need to accomodate the drop you have, and see if you've got enough left over to handle the horizontal shift.
Others here may be able explain it better or correct me if I've interpreted the info incorrectly. Bottm line, this calc method worked for my installation.
I have the RS-50 nestled pretty close to the ceiling on the Unistrut mount that held my G70 for 10 years, and the lens shift has enough range to cover my drop and then some. No issues with distortion, no electronic adjustments needed.
P.S. you can download the IM from the JVC website.
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