That's why the heavy tubes, thanks. The bike is completely unknown in Holland here, though, so it's fun restoring. i'll strip the frame completely, repaint in the original orange and start rebuilding. I have here a Shimano RD-M 520 Exage ES derailleur (from roughly the same period) and the original Shimano Biopace SG 28/38/48 crankset seems okay.
Any tips for the gear?