Just raise the level for 3x Lumber, that will give you more EXP at the same more difficult (and make sense, if you are trying to process some times 3 times faster than normal, isn't it more difficult?). What you don't realise is that crafting EXP is based on difficulty, or rather the level difference between you and the recipe. Same level of difference give same amount of EXP. You may want to have the 3x Lumber recipe remain the same difficulty but give more EXP, that won't happen. What did people say about PL that they are fixing today?