Hi, Welcome to satellites,
It would not be possible to increase the overall gain sufficiently with two 1.25m dishes to equal that of a 3.5m one. You would need about 7 of them. Apart from that it would be very difficult to get the phases of all the signals aligned properly. I imagine the equipment needed even if it was possible would cost more than the 3.5m dish that you say you need. Give it up a as a bad job m8.
Robbo
