For quite some time I have been tinkering with an idea to get into the ultra large format photography one day.

What troubles me is limited options for the color film. I love color photography.

I understand that the possible options are

1) Kodak Portra up to 11x14 (or more?) but this requires either very large investment (to order the minimum quantity) or luck to somehow get some from somebody who has made this investment.

Does anybody know what is the current state of this affair? Would it be realistic to acquire true color ULF film in small quantities?

2) Color paper negatives. I have seen that some people have gotten very good (in the sense of the color reproduction) results (with smaller formats).

Has anybody tried this with larger photo papers?

3) Trichromatic photography. Are there practitioners of this in ULF? It would probably provide a more easy path to correct colors (compared to the photo papers) if the subject is cooperating (edit: unless a special camera with 3 films is used). Is my thinking right here?

4) Finally it should be at least theoretically possible to make a home made color film based on layered black and white films and color filters. Chromatic aberration would be probably problem with this method because of the film thickness. Is this thinking way of the base?