If it's like the I-O, the NUMBER OF CHIPS on the SoDIMM is the determining factor.
The IO couldn't address above 16M per chip.
The 128 MB module with eight 16-M chips worked, the module with four 32-M chips DID NOT.
Some reports said the 4x32 showed up as only 64 Mb. Other reports said it wouldn't boot at all.
By analogy, you would want a 256 MB module with SIXTEEN 16-M chips. Never seen such a beast.
Of course, this I-O lore may not apply to GCT. I'd be delighted if that were true.
If you take the gamble, PLEASE report your results here.