HD-1000 Memory expansion?

The HD-1000 seems to have four (4) K4D261638E DDR DRAM devices, two on
the top of the board and two on the bottom.  Did the board designer
allow for them to be replaced with, say, four K4D551638D devices to
double the amount of memory?  And if the board designer was that
forward thinking, was the firmware author also as forward thinking?
:-)   My crew is no stranger to this sort of hardware operation, we've
upgraded the memory on Tivos, Palm V's, iPaqs, etc.,

I'm guessing that half of the current memory is used by the
framebuffer so the end result would be 3x the current memory available
to software...

Cheers!greg