DOCBOOK-APPS: Using DocBook 4.1 with FrameMaker+SGML 6.x

I've been using the DocBook XML DTD for a while for various projects;
recently, I thought to improve my working interface by acquiring FM+SGML. I
assumed I'd have to switch over to the SGML version of the DTD, but when
trying to set up an SGML app in the environment I get a long error list on
importing the DTD and an empty element catalog. Is there something here I'm
missing? Can the DocBook/FM+SGML combination work for the current versions
of both?