Can't install bootloader on H340

[askvictor]

I'm trying to revive an old H340. It was previously running rockbox successfully, but I wanted to change to a flash-based HDD, which wasn't working, so decided to upgrade the bootloader. Unfortunately, any bootloader I flash just seems to install the stock iRiver firmware. I've used the rockbox utility to mod the downloaded firmware (I've tried a couple of them), install the firmware as directed, but then it just boots back to the stock firmware (I can tell it has in fact installed the firmware as the version changes). After modding, the .hex file is larger (~4Mb compared to ~2.5Mb for stock), so it's being changed. Any ideas?

[Frankenpod]

Could it be that the flash-based adaptor has similar problems to such adaptors in ipods?  i.e. rockbox's drivers don't play nicely with flash drives?  Or are you now having trouble even with the original hard drive?
(I know nothing about H340, hopefully someone who knows about that player will come along, just wondering if it's the same sort of issue that can come up with flash drives in ipods).