Converting Pistol X bows into Carbine X Bows ???

[NorthernRaider]

Can anyone think of a way of modding the 80 pound Tomcat / Cobra Mks 1 & 2 into a carbine sized weapon like the Taipan?

I'm trying to think of ways of making and fitting a shoulder stock to the rear cocking lever that is the back end of these natty little pistol bows, any ideas or plans welcome.