There is a working patch for the Sharp development board, KEV7A400 available here. It's a little too large to make the 40KB limit.

ftp://ftp.buici.com/pub/u-boot/u-boot-0.4.5-1.diff.gz

There is also a binary for those who would like to test it.

ftp://ftp.buici.com/pub/u-boot/u-boot-0.4.5-kev7a400.bin

Cheers.