Shinjyo recipe help

I was trying to make shinjyo (fried shrimp balls) for the first time today. The recipe I was using came from the "Japanese Cooking" cookbook by Emi Kazuko and is also online here if you search "shinjyo recipe" on google (I don't have enough posts to do links apparently )

Although I made something that was quite tasty, they definitely weren't "balls" by any means. Even adding 3x the cornstarch called for, it was quite liquidy (like thin pancake batter).
Has anyone made these before and knows what the secret is?

Prepare the Shrimp Batter:
2 Tablespoons potato starch (or cornstarch)
2 Tablespoons water
8 ounces peeled, and deveined shrimp
8 ounces cod
(I had 4 ounces cod and 4 ounces salmon)
1/2 teaspoon salt
1 – 2 egg whites
2 Tablespoons finely chopped Chinese Chives
Ebi-shinjo: Shrimp Dumplings

Click to expand...

I noticed that he does not use any Yamaimo or Yamato Imo in the recipe.

One easy substitute idea is "cooked rice, lightly mashed". Just mix this with what he call the batter.
I cannot tell how much rice you need, so start from one ounce of rice. Add more if you need more thickness.