FT817 Frequency stable enough for QRSS?

Having previously seen how unsuitable the KX3 currently was for WSPR and QRSS modes I was interested to see how my equally small FT817 would perform. It is fitted with the factory standard crystal oscillator (not the TCXO-9 option). I found the audio cables and the isolation transformer box and it still seemed to work in digimodes.

Last night I ran it as WW2R on 30m into my alpha Delta DX-EE antenna (sloping NE) at 20'.  As a comparison I also ran the ARDMEPT as N4FRE on the Butternut HF6V Vertical. Both rigs produce 250mW and both transmit evey 10 minutes. Using the W4HBK grabber to monitor the signals 1000km away over a 4 hour period and I saw the following result:-

The upper signal (~10140080Hz ) is the GPS locked N4FRE. The lower signal is the WW2R FT817 signal (~10140030Hz).  As can be seen the FT817 frequency stability is acceptable for this mode. It is also interesting to see how the path fades out overnight. 
Now I have another compact way to get a signal out on QRSS,  although unlike the KX3 it will need an external ATU.