I use a DIY version, and I'm happy. My suggestion is to slowly come up to your target dose. I believe if you start out at the target dose, you have a better chance of feeding unwanted bacteria.
As far as methanol, it's only present at very low concentrations, and I'm convinced that it's only there because it is the "denatured" component of the alcohol they are using (denatured alcohol is not drinkable, and therefore not subject to the alcohol tax.) I believe methanol is only consumed by anaerobic bacteria. FYI, I have no methanol in my DIY version.