You should NEVER EVER use keystone.
I have seen several installs where a company used keystone on a home theater install. I took over the jobs because customer was complaining about picture quality. When I discovered what they had done, I had no problem throwing them under the bus. Any self respecting installer should know not to ever use keystone in a home theater. This isn't up for debate, it is a fact!
Keystone is for board rooms and portable projectors showing slide shows.

If lens shift isn't working, then you have another issue.
If it is working but not giving you enough movement, then how high above the screen are you mounting it? Or like others have said, you are not mounting it right towards the orientation (upside down if above the screen). Besides using a ceiling mount inside the hush box, if space is tight, they make slide plates for projectors to go inside hush boxes. They are made for this very reason.

[edit]: I came back, as I see the 1st part of my posting seems harsh. It's just that you have been installing for over 30 years, as far as I know. You should know these things. And for you to rant about a $25K projector 'not' having keystone, just dumbfounded me. I can only guess you just has not done very many projection installs in your time, so you never felt the need to learn about them.
[edit2]: Or maybe only experience from the CRT projection days, which keystone on those monsters was completely different. You were physically changing the scan lines and convergence when doing keystone. Which didn't impact on the picture quality like modern digital fixed resolution projectors do.