Technicals and Guntrucks

[Rheged]

Does the rider sit ASTRIDE the recoil-less rifle? 

Yes.  Its actually angled, to clear the steering column.  It was though, used dismounted.  Another Vespa carried ammunition and the tripod.

http://www.ospreypublishing.com/blog/Scooters_From_Hell/

As Little Richard is reputed to have sung  "Goodness  gracious great balls of fire........!"

[Mossie]

IIRC it could be fired on the move or the bike used as the mount if speed was of the essence, although this wasn't exactly SOP!

[Go4fun]

Now if someone mounted that or a Squad Machine Gun on a Trail Bike, Quad Runner or a Crotch Rocket things could get real interesting. 

[ysi_maniac]

What a whiffing idea: aerial rocket launcher mounted on a truck. 

http://www.britmodeller.com/forums/index.php?/topic/234914672-135-ural-rocket-guntruck-broom/