Modification is completely reversible, and almost cost nothing - all we need is only 2pcs of 1,5kOhm SMD 0402 size or just ordinary carbon film resistor 5% accuracy.
This will allow us to key two first banks of memory signed M1 and M2
First open the case and locate copper track leading from switch DN through 470Ohm resistor to UP switch and down low the microphone PCB to output solder point - red wire.
Next cut the trace from "UP" switch leading down to Red wire and remoce green mask for soldering second 1,5kOhm :
Because UP/DWN switch using the same pin3 in Microphone plug, no resoldering is needed.
Now "UP" switch is acting like M1 bank and "DN" switch as bank M2
Shouting in pile up or run local Contest without wasting your throat or making your wife angry :-O
should be much easier now...