Emax

Hi all. As an Emulator II user for several years (see YT JMPSynth), decided to take the plunge on an Emax II Rack, 2MB RAM with internal 500MB HD. I see its advantages, particularly with a SCSI zip drive attached and currently delving through the Emax II library, experimenting with EMXP conversion utility etc... 

Anyway, one question, whilst the HD is 500MB and shows a large space available, I only seem to get approx. 100MB used before out of memory/space messages. Presume that's normal? Have tried to clarify this searching here and in the manual but can't find confirmation of it.     

Looking for a replacement FDD for my Emax II if anyone has one for sale or an easy install replacement. I've seen the slim Mitsumi one listed here but not sure where to find the adapter face plate.... People made their own? 

Ta.