Thanks a lot for this trick to make a sushi..
My tip for you is sparing use of rice than you think. For nigiri-zushi, the rice should be a bite size not bigger than that. Gorgeous nigiri-zushi is difficult to eat. Also, for maki-zushi (nori-roll), you should put amount of rice sparingly. If not, you can't wrap strip of tuna (or salmon or cucumber) and rice up together completely. If you tired of failure making maki-zushi, try témaki-zushi (pictured). This is a lot easier.