I have also been considering methanol injection on mine. From what I understand, the most beneficial gains are made when the methanol injection is actually producing the appropriate AFR, while reducing the amount of fuel through the carburetors.
On a stripped blower, at least 70% of the fuel needs to pass through the blower for lubricating the strips. Unless someone machined your rotors for strips, your blower should not have that issue because there is actually clearance between the rotors and the case.
On my engine, I think I am near the limit of my 6-71. I don't think I have enough engine to substitute methanol as enrichment AND reduce gasoline passing through the blower while still maintaining sufficient lubrication for the strips. This is assuming that the methanol is injected under the blower.
If the alcohol passes through the blower, it will chill the rotors and actually cause them to contract. This will open the clearances and and increase leakage, reducing blower efficiency. A lubricating additive would also be required for lubricating the strips (not a problem for your blower).
Another minor issue is that methanol is caustic and badly corrodes aluminum. Normally, everything that comes in contact with the methanol would need to be hard anodized and/or coated to prevent corrosion. Subsequently, the whole methanol system will need to be flushed at the end of every day.
You are looking at the under-carb plate system. I am not convinced that that is the best location for the injectors, mainly because I don't want to subject my blower to corrosion like that. Also Roots blowers don't have an internal compression ratio like a Whipple screw type blower. I think the best location for injectors would be under the blower. In your application, I would put them directly pointing at the port opening, as high in the manifold as possible. This would provide sufficient time for the "cooling effect" to take place and bypass potential issues with the blower.
If simply using water/methanol injection for cooling purposes only, you are leaving performance on table.
With all that being said, I keep coming back to the air-to-water intercooler. My decision, after weighing all the above, it boils down to; I don't want to have a secondary fuel that is required simply to drive to the cove and back. Almost the same as why I didn't want to run N2O, I hate filling bottles.
