Limited specs announced for the Optoma 4k UST suggest a maximum 3,000 lumens and maximum screen size of 140" diagonal. Your 20' wide screen would have a diagonal of 260" which is beyond the design limits of a 3,000 lumen UST projector.
As with your other thread about using 4 projectors on a 20' wide screen it appears that you are just brainstorming wild ideas without having any real experience or knowledge of the fundamental technical issues inherent in video projection.
Screens as large as 20' wide and projectors that can properly fill them with an adequately bright, quality image are expensive. Before going any further it would be good to know exactly how much money you have budgeted for this project.
Last edited by Dave in Green; 01-18-2017 at 03:37 PM.