did the Rex cartridge also working with the generic (universal 8k image) option. thanks tom for the addition
Edit:
regarding the tapecounter, found the isssue in the src code. default UI is xaw. but there is "--enable-gnomeui" as a configure option: ./configure --enable-gnomeui
this does the trick, gui is bit nicer and tapecounter is working
Edit#2: have a look at:
http://tapes.c64.no has some *.tap files. tried Uridium(+) for example. loading like real tapes. funny thing, using a loading bar - cant recall this