From what I’ve read alcohol will tolerate a 14:1 ratio, which is close to the limit for woodgas (17:1). If you went 14:1 you should have no trouble getting “starting fluid” as E85 becomes more popular. There’s 3 stations within 30 miles of me.
As far as “optimal power” you’d have to do a lot of testing to be sure. I have heard conflicting reports on “slow burning gas” and “3,000 RPM limit”, and then Sean French takes it to 5,500 and holds it there on the highway. The hydrogen is thought to burn faster and the CO burns slower? So depending on the makeup of the gas you will get different flame qualities.
Another factor has got to be the air/fuel ratio. We are blessed to have a wide range of acceptable mixtures, and so mixing is done by hand. But if you’re optimizing already. I’d go for an O2 feedback system to automatically control the mixture. Alternatively, Dutch John has used a pressure equalizing valve to make sure the engine gets a balanced pull on the air and woodgas, he sets the mixture once and the valve takes care of the fine tuning. I don’t know if he’s running any sort of feedback though.