As it is a small guide deviation, do it at very late, after checking if everything works as it should.
Each patches must be installed under is normal counterpart except Experience's one.
You will need to install patch from the mod Complete Widescreen Fix for Vanilla and SkyUI 2.2 and 5.2 SE. (Don't forget to endorse it)
- Complete Widescreen Fix for SkyUI 5.2 SE Alpha - 2560x1080
- Experience - Widescreen fix (merge with previous one)
- SkyUI SE - Flashing Savegames FIx - Widescreen Fix
- Opt. 1 - Wider MCM Menu for SkyUI - Widescreen Fix
- Better MessageBox Control Widescreen Fix
- Campfire 1.12.1 and Frostall 3.4.1SE - Unofficial SSE Widescreen Fix
- Move Minimal Oblivion Dialogue Menu (Moded EZ2C Dialogue Menu) & Better Sleep Wait Menu just right under Complete Widescreen Fix for SkyUI 5.2 SE Alpha
- Replace dialoguemenu.cfg content by content of the one uploaded here
You will need to adjust frostfall mcm value, as the ones given by the guide don't fit well with an UW screen, same with Matter of time.
(I will give mine on next update)