I dont know if there is a size limit in GB's but the physical size of the drive is crucial , ie: there ain't no room to spare. For some info on zif conversion's check out
ZIF connector drives on H320/H340 and stolltech"s web site
http://www.stolltech.ch/i_projekte.html (click on the iriver pimpen pdf link in stolltech's site) you may need to use bablefish or similar to read the site.