First, here are the 4 figures I used for the conversion. The one on the left is from HYEN02 and the one on the far right is the chieftainess from HYEN05. The two riders are the poses from HYEN07.
Second, I took an xacto knife and some heavy duty nail clippers and cut these four figures in half. The nice thing about these poses is that they divide very easily and without too much mess.
Next, I glue the halves together. I use zap-a-gap. Though the halves do not really look great lined up, I have found extra glue and a coat of primer really takes away the obvious dividing lines.
Fourth, I glue them onto their mounts. I know there is a variety of thought on this but I like glueing the metal to metal and then painting the mount and rider while attached.
Fifth, I glue them onto a craft stick and prime. Note how the dividing line largely disappears (if you can with the horrible picture!!).
Finally, here is the finished product.
I have done lots of these types of conversions and find them easy and fun. I have replaced sword hands with spear hands and have also drilled out hands after clipping weapons to turn a figure into a standard bearer. At 15mm, it is easily done and looks great.