Marco:

Presently, Chirp communicates with the Yaesu FT-897D only in clone mode.  It's been quite some time, but as I recall, one can read/write memory in the FT-897D (and I think the FT-857 and FT-817 series as well) using two commands (one for read, and one for write) that provide a radio memory address and just transfer just two bytes of memory.  As I recall, it was reasonably quick if the timing was right, to transfer significant amounts of data in a short time.

Are you planning to make that kind of change to Chirp?  That would be more convenient for users than going into clone mode.  On the FT-897D, you have to press two ("MODE") buttons that are very close to each other and also close to a knob, as you power on the unit. It's a little awkward, and even more so if one has fat fingers (I don't).  Then, if you accidentally remember the wrong pair of buttons and press the two "BAND" buttons just below the two "MODE" buttons when you power on, the radio executes the diagnostic "relay cleaning" operation.

Just another "wild" suggestion ...