Typical multiple axis accelerometers today are quite small -- often 3mm x3mm (i.e., QFN 12 or 16 packages). So, finding a place to put the chip is not that hard. However, you do need to consider associated circuitry, and it seems unlikely and difficult that you could fit that onto an existing PCB.
I recommend that you design a PCB with MCU for your project. Then, it can be mounted piggy back onto an existing device such as the receiver.
Are you are considering a mulit-rotor copter like popular drones or a single rotor helicopter?