Small English 4th Rates had a mixed lower tier of guns

Small English 4th Rates, at the time of the Four Days Battle had mixed armaments on the lower tier. That seems to be because they were perceived as being too small to have a complete lower tier of culverins (18pdr). For example, the frigate Assurance, built in 1646, had a lower tier of 10-culverins with the remainder being demi-culverins (9pdr). The upper tier was partially armed with demi-culverins, with the waist apparently unarmed. She had 10-culverins, 24-demi-culverins, and 4-sakers (5-1/4pdr). The sakers were apparently on the quarterdeck. The dimensions of the Assurance were: 89ft x 26ft-10in x 11ft, giving a burden of 340-81/94 tons. I estimate her gun deck length to have been about 110ft.