I have a poster I want to mount. (not a photograph) Light weight paper, slightly thicker than magazine print. It's about 20x24 and was wondering what would happen if I used 6 sheets of 8x10 tissue on a mat board and was careful to butt the edges. Or 1/8th inch overlap? My press will cover 20x24. Tack iron to hold in place. Looking to minimize/eliminate any line or transition between tissue.

With the butt edge will the seam melt into itself?

With the overlap will the bump flatten?

I assume thicker fiber print would work better but might still show a line where the tissue overlaps/butts? (is this forbidden? )