My current sdnet.config:
TIMER=7000 SPISPEED=2 MTU=1492 FULLDUPLEX
SMB uploads continue to fail as described earlier.
However; using FTPmount, uploads to the same directory in DOPUS works just fine and is very fast.
So the issue is now down to smbfs.
version smbfs 1.102
smbfs script to mount the share
Run >NIL: smbfs workgroup=FEDCOMS service=//FEDCOMS-NAS/Amiga user=*MYUN* password=*MYPW* device=ANAS: volume=AmigaNAS: