Not specific to Maemo or our beloved n900's by any means, but does anyone know how to disable file preallocation on Samba?

I've searched through all the documentation and a bunch of threads that discuss the issue and found nothing, but I thought some of the great minds here might have figured it out.

For those who are wondering - Samba preallocates files per client request. That is, if you drag and drop a 500mb file from your PC to samba on your phone, it'll start by extending the new file to 500mb before even copying any data. On ext3, not a problem - a sparse file is instantly created. On fat32, it zeroes out every last byte. This takes a while, so for large files causes a CIFS timeout.

I'd prefer not to switch MyDocs and mmc1 to ext3 as I occasionally mount them on a Windows box via USB mass storage mode.