Split block_heads_1_16.yml into 2 parts the old 107 blocks updated to work in 1.16 are in block_heads_1_16.yml the new blocks are in block_heads_1_16_2.yml the max of block heads is devided into two, each block_heads file getting half the chance to be added to custom trader. So 5 will get 2 and 2, but 8 will get 4 and 4.