As you know, when we japanese chant, we sit on the floor Japanese style generically.
It was called SEIZA(to sit straight with your legs folded under you./kneeling).
I had trouble in Seiza because I could not feel my legs.
Also, many young people have toruble in Seiza.
When I had begun to pracitce, I did not always chant toward Gohonzon.
To what did I chant?
I used to chant toward an occipital region of head of our leade.
Then I paryed in my heart like this.
"Please, tinkle a bell early and finish chanting Daimoku. Or I may die....Oh, I can't feel my legs!!!"
When chanting finished early against the odds, I used to feel happy.
And I thought "Oh, my dream came true! My Daimoku made our leader trinkle a bell!"
I used to feel envy when I saw overseas members chanting sat on the chair.
Now I use Seiza-chair which is very small chair under my hip.
However, I am to use normal chair when I chant more than one hour.
Off cource, I chant Daimoku toward Gohonzon now.
Nichiren and Sensei are not saying that we should not use chair when we chant.