Tried now to hold the key in one hand and work the other 
Seems to be okay’ish, but no more than 15 wpm though! A pain in a pile up … as I will have on 2m for sure
Another idea is to get my USB Plantronics headset converted and try to VOX it for FM/SSB semi hands free.
The pile up will be so fast and frenetic that your hand will blur and flames and smoke will begin to emit from the key. 
While making and testing a headset, I’ve noticed a nasty misalignment in the FT-857. Transmitting in SSB had a noticeable carrier present on a background. A quick browsing on the net pointed to a carrier balancing variable resistor VR5 on the main board (as easy as to take a top cover). That worked 100% I’ll leave the picture of the adjusting element here for reference in case anyone experience a similar issue.
