Removing the shock protection would make larger batteries fit too, but it could be compressed on mine to make the 2nd Gen iPod 2200mAh battery fit.
Speaking of which, I salute anyone who's had have to change the batteries on the H120/140.
The allowed space is so darned constricted its not funny x_x
Because what I used is 2nd Gen iPod battery, I had to switch the polarities, but being in school afteer I got my Torx set, I had no access to proper soldering tools. After a long operation of cutting the connecting wires iPod battery and iRiver battery to a certain extent, it was a long and nerve wrecking operation to tie the cables into place with my large clumsy hands x_x
The exposed parts of the wires were sealed using leftover tape from the old battery, since I had no useable tape at the time x_x
Placing the connector back was also very difficult, so I had to cut bits of it off to make it slide in better.
Thank goodness that the unit wasn't damaged by any form of static durng the near 2 hour operation (don't laugh, I'm not familiar with circuits and such >_>

, the unit was re-assembled and now has a 2200mAh battery installed.
What's left is installing a large capacity CF drive into the player, as I only have a 512MB one with me right now.
Anyone in the US willing to help me get a 32GB A-Data CF card to help me complete my quest? I can't get it from Newegg since I'm in Canada. I can pay anyone who's willing to help via Paypal =)