Seeking implementation advice on WFC:PE Between Declarations in Production

Because I know that several of you out there have implemented this 
(okay,  based on some conformance results only a few of you...) I was 
wondering if anyone cared to offer some advice on implementing the 
WFC:PE Between Declarations in Production [1]. My main question is this: 
can you simply check that the entity doesn't start a declaration and not 
finish it? This would be similar to the implementation of VC: Proper 
Declaration/PE Nesting [2]? It seems that the only two cases where the 
VC and WFC are not redundant is that the WFC adds the additional 
constraint that a PEReference (the actual ref, not the replacement 
value) cannot be started in one entity and ended in another and that a 
conditional section cannot be started in one entity and ended in another. *

* I make this claim because the VC refers only to markupDecl and the WFC 
refers to extSubsetDecl which includes (markupDecl | conditionalSect | 
DeclSep).

[1] 
http://www.w3.org/TR/REC-xml/REC-xml-20040204-review.html#PE-between-Decls
[2] 
http://www.w3.org/TR/REC-xml/REC-xml-20040204-review.html#vc-PEinMarkupDecl

Thanks again for any guidance... I really am almost done asking all of 
these questions : )
Jeff Rafter