I use the Procede with meth, but mounted the pump and tank in the trunk. I don't have any concerns about an engine fire.
I did initially install the system using the washer fluid tank and mount the pump in the engine compartment, but I did not like the washer tank's proximity to the hot headers, the chance of a flammable splash during refilling, using the expensive and highly concentrated meth to clean the windshield, the way the pump hung in the PS reservoir hanger, or the way the PS reservoir dangled in its new location.
I bought my first water/meth kit in 2001 and have never had an engine fire. While I am using a flammable mixture of 70/30 meth/water on the E90M3, you can reduce the mixture to 50/50 and it will not be flammable.
I don't think the mixture of race gas to get your pump fuel to 95 octane will yield the same octane as the meth does when it is flowing. The meth is also the cheaper form of octane enhancer. Even if I used a gallon of pure meth per tank of fuel (I would roughly estimate that I go through a gallon of diluted 70/30 meth/water every three tanks), the cost would be $7 versus the $35 for the five gallons of race gas needed to add to 10 gallons of 91 or 93 to get the tank to 95 octane.
The number of cars with bolt on mods and tunes breaking 400 rwhp SAE on a Dynojet is still just a handful. In contrast, there are many making 380-390 rwhp. Higher octane, whether from meth or race gas, will certainly help a little.