moving label of arrow

Question

How can I shift the F_{2}(f') label so that it isn't touching the arrow?

 \usepackage[all]{xy}
    \SelectTips{xy}{12}
    \[ \xymatrix{ A \ar@{<->}[rrrr]^{F_{1}(h' \circ g')} \ar@{<.>}[rrd]_{F_{1}(g')} \ar@{<->}[dd]_{ F_{2}(f'')} &&&& C \ar@{<->}[dd]^{F_{2}(f)} \\
    && B \ar@{<.>}[rru]_{F_{1}(h')} \ar@{<->}[dd]^{F_{2}(f')} \\
    A' \ar@{<->}'[rr]^{F_{1}(h \circ g)}[rrrr] \ar@{<.>}[rrd]_{F_{1}(g)} &&&& C' \\
    && B' \ar@{<.>}[rru]_{F_{1}(h)} }

Answer 1

You can say explicitly at what position along the arrow to put the label:

\ar@{<->}[dd]^(.35){F_{2}(f')}

The default position is (.5)