Look at the readme in
http://www.pdp8online.com/ftp/software/dumprest/README.TXT
You will need to download one version of the original package, the best for 
modern windows is dumprest_cygwin.zip and tc08.zip for the TC01/TC08
pdp-8 programs.
Extract them in the same directory. Create dumprest.cfg as
described in the readme
To write a tape get an image file. You probably want my bootable TC08 tape
http://www.pdp8online.com/ftp/images/os8/tc08diag.tu56
download resttc08.bin to the PDP8 with bin loader and either my sendtape
or the method you have been using
at the pc run the command
resttd8e tc08diag.tu56
start the PDP8 at 200
Hopefully it will write the tape

To dump the tape
download resttc08.bin to the PDP8 with bin loader and either my sendtape
or the method you have been using
at the pc run the command
dumptd8e filename.tu56
start the PDP8 at 200
Hopefully it will read the tape and save it on the PC. This will be in
the format of all the images I have online. As long as you haven't
booted the tape the dump of a tape should be identical to the tape you
write.