How much thicker will the mattress (shikifuton) be if I add extra cotton?

In reality, there is not much difference in thickness. If you think the futon may not have enough support, we recommend placing a futon topper on top of the futon.

Extra Cotton Filling Ticket for Futon Mattress 0.66lb (0.3kg)

Futon Topper (Thinner Shiki-futon)