(b) The maximum ultimate strength of the hatchway cover material must be at least 4.25 times the maximum stress in the structure calculated with the following assumed loads:

1. (1) For ships 350 ft or more in length, at least 250 lb/ft ² in position 1 and 200 lb/ft ² in position 2.

2. (2) For ships less than 350 ft in length, at least AL in the following formula:

   1. (i) Position 1:

      AL = 200 + C

      where C = 50(L−79)/271

   2. (ii) Position 2:

      Al = 150 + C