Can the HP-12C's program memory be upgraded?

[lvt]

I would like to know whether it's possible to upgrade the 12C's memory, just like with the 15C?

I actually have two 12C, a regular and a 12CP.

The 12CP has plenty of program memory, but the CPU is so slow that it takes a very long time to scroll the lines in its memory. I have to manually press the SST button to find the line that need to be edited. And when the number of program lines reaches 300 or 400 lines, it's a very tiring thing to do, both for the owner and the calculator's SST key.

The other 12C has a very fast CPU, it can reach the 99th line in no time, and from what people say it's upgradable, so I think it would be great if the 12C's firmware can be upgraded for more memory, even a couple of extra lines would be immensely useful.

For example, a custom firmware with a patch that converts the remaining registers (R0 - R6) to program lines when needed, so a program memory with 128 lines would use 18 registers, leaving registers R0 and R1 for the owner.