Well, it varied very significantly model to model. Some of them are what I'd call smart use of existing poses, like the guys using the 6th edition unipose handgunner bodies (middle of the front and back rows). The guy in the middle row farthest to the right took some precision (and greenstuff) to do, to get the left arm (6th edition halberdier arm) to match with the crossbow.
The guy on his left, the guy in the furry hat who's winding up the crossbow, he's the kind of conversion you're happy you did but don't intend to do again. Since none of the bitz I had available either crouch or kneel, it was a challenge to get him to actually reach the handle on the loading gear (don't ask how he can turn it all the way around...). To get the crossbow close enough to his body, I had to realign his left foot a bit, add some greenstuff to the back of the interface between the torso and the legs so he'd lean forward a bit, as well as use greenstuff to slightly elongate his right arm where it connects with his hand, which is a 6th edition militia archer hand that originally held an arrow, now it's holding the handle on the loading gear. If you're interested, I could take some close-up photos of the conversion.