XF 1.2 How can I change the width in the preview mode?

Hi all!

Lets see if I can explain myself ;).

Im creating content in html with a maximum width of 800px. For example I use two images one next to each other of 398px width and work greats. The same with one 800px width. The issue comes before creating the thread or post, when I do use the preview option. Seems that only 780px of width are available of use so I do not see the images properly. Yes, after creating the thread or posts works but not in the preview mode. In the image attached you can see the file with a 780px but originally its 800px. Also you can see an example of preview and created.

How could I set the preview mode to 800px width?

-I tried it with and without addons
-I tried it with standard xenforo editor
-The style is set to responsive

My extra.css only contains this:

.sidebar .visitorPanel {
display: none;
.mainContainer {
width: 128%;

The page width controller:

Thank you in advance and sorry for my poor explanation. Its my first time playing around with css...

Test link http://www.theacp.com/index.php?threads/test.119/




Style Properties -> Forms -> Max Form Width

Increase it from 800px to whatever you require.

Hello Brogan, I been looking for this, glad I found this thread.
Can I also just let the field for max width empty?
I did try it, and then I just get it how the width orig. is.
Should not cause any problems to leave the field for max width empty?
Why do you want to leave it empty?
What are you trying to achieve?
My moderators did complaint that a post/thread preview is not giving the true view.
I played around a bit, and found that if I add 98% the preview looks same like posted live then.

Since we posting reviews with images and more content, it is useful to see in preview how it looks.

Do you think it is ok to add a value like 98% ?

Thank you