From my knowledge, which is limited, as long as you can match the flow from the eductor, yes. The issue may be finding a 2 1/2 line that flows 125gpm. And then the other question would be if that is your target flow rate, why use 2 1/2.
We do it with 1 3/4 with no problem. And if you are pumping the eductor at 200 psi, you will make foam, the quality depends on matching the flow rates......
You can use 1.75" hose. The only difference will be the distance from eductor to nozzle can be longer. We use a 95 gpm eductor with 1.75" hose and can "theoreticly" use 250'. The most we use is 200' and have never had a problem. We also use automatic nozzles without a problem. You just have to have them ALL the way open.
If you have an around the pump proportioner you can flow foam out of every discharge. You could pump foam solution through 4" or 5" supply line to another truck hundreds of feet away.
William: Thanks for letting me know that. We have never used any type of class B foam on anything but training. The only Class B foam that we used in training was going to be thrown out because of the age and it was a 3% - 6% AFFF foam. I didn't even think about the ethanol used in the gasoline. Without the AR-AFFF foam it would be very hard to suppress these new fires. Especially the new flex fuel vehicles. I ended up talking to a guy that has one and it will run on just ethanol or the ethanol gasoline mixture. What about using FireAde? I heard that it is not corrosive and is biodegradable and that it knocks out all parts of the fire tetrahedron by emulsifying the fuel.
Like I said, thank you for bringing this up. It didn't even cross my mind.