I have tried to use the set Xfermode to change between Binary and Ascii modes, and even checked it with the fetch command, fetch returned a 0 if Binary was selected, a 1 if ASCII was selected, but it did not seem to have any effect on the mode.
Here is another way you can try, using the Menuselect command which
Selects a Procomm Plus or ASPECT menu item.
Proc Main
#include "pw4menu.inc"
set ftp filter local ""
set ftp filter remote ""
ftp local chdir "c:\program files\procomm plus\backup\"
Menuselect PWMENU 18120 ;see pwmenu.ini file in the aspect directory, this selects Ascii on the toolbar
pause 5
ftp remote copyfile "ASCII filename" ;copy file from the remote ftp site
while $ftpstatus ;Yeild while transferring
yield
endwhile
PAUSE 4
Menuselect PWMENU 18119 ;see pwmenu.ini file in the aspect directory this selects Binary on the toolbar
pause 2
ftp remote copyfile "Binary file name" ;copy file from the remote ftp site
while $ftpstatus ;Yeild while transferring
yield
endwhile
hangup
endproc