Hi Pighood, If you update the OS you will loose any custom patches/waves you have created(see below). It is always a good idea to keep a backup of your Project ie all the patches and waves.
There is a section on data management in the FAQ which covers adding patches to existing projects.
http://v-tribe.info/documents/V-Synth-FAQ.html
edit
this is a quote from the 1.51 upgrade
"In the Ver.1.51 system program, due to the renewal of the
Preloaded Memory (additional oscillator Waveforms, Patch
Category function implemented), the Preloaded sound data
(V-SynthDiskImage.bin) must be updated at the same time.
Update procedures are the exactly the same as the system
program, however unlike updating only the system program,
Factory Reset will be automatically executed to the data
inside the Internal Memory.
Due to this fact, before you update, data inside the Internal
Memory must be saved to a PC Card, or copied onto a PC via USB
for back-up."
For peace of mind back it up, upgrade, then rebuild your project with your custom patches etc.
Regards and all that