I see a lot of PJ builders here in europe using threaded rods in their pjs. I know one use of using rods is to be able to adjust the light engines and optics to the ideal focal lengths and image tweeking. However is it possible to do some keystoning with the rods. For instance having some parts of the front fresel closer or further from the lcd by adjusting the nuts or will this break the fresnel.

Cheers

I think that's what he does in this thread:

Pun15hers design

You can use "Lens Shifting" to keystone. It gives you all the benifits of an unsplit setup with keystoning. The down side is that you can't adjust the keystoning after the box is built, but if you aren't moving the projector around (remember... it's going to be really big) than that isn't a problem. I'm using it in my projector and it works very well, I get corner to corner (and center) focus and an arguably more evenly lit projection.

It will stress the fresnels if you try to do it with a rigid frame. But if you make the holes large enough, then you can move them with no problem. You just want to make sure that when you tighten them you dont put any stress on the fram because it will translate some of that stress to the fresnels.
I designed a rubber grommet system for doing this which works well and will provide 4 way keystone. Really easy to make. Most folks go with the gravity keystone. I also designed a gravity keystone for vertical pj's.
Im lazy when it comes to keystoning...

Verticle pj gravity keystoning? That sounds interesting...

Vertical Gravity Keystone adjuster

If it works for you , fantastic!