Read with interest about PE conjugated secondaries or even primaries 
are not suitable for IHC work.  We do them here, but the scope setup
is a new Inverted type with IFA capabilities and the PE is brilliant on
tissue sections, we do PE conjugated-CD4 and CD8, rat antimouse with
cleaner results that FITC or TRITC. These primaries are often used for
FACS work, but having the PE capability on inverted scope (has adaption
to read tissue sections besides culture flasks) is very versatile.

Might be worth a check to see if you have IFA inverted microscope around,
interfaced to a computer no less, with PE excitation capability
A regular fluorescent microscope will not work as well with PE.

Gayle Callis