This is indeed a great thread! 
Pease see the write up to the artwork below at 
https://en.wikipedia.org/wiki/Jezail...fghanistan.jpg also included in a previous post at #25. Note in this painting the almost invisible two bipods shown on the right hand side of the artwork. These bipods were needed to offset and support the front heavy, long barrels of the jezail but not on all. Often these weapons  were made with captured brown bess locks or converted to flintlock from matchlock later.