I have only found an FT4 QSO on 10.140 which seems mostly abandon all day long.
I have listened to 7.090 and called CQ in FT4 with no luck.
Where are the FT4 experimenters on 80/40/20/17? 
I have looked at the suggested frequencies (3.595, 7.090, 14.140(SSB) and never saw/heard an FT4 signal.
mny tnx,
72/73 de Ken N9VV