Hi Sophos9
The reason I hadn't answered your email is quite simple.... I didnt know the answer.
My apologies.
Having never worked on the DM4, or had a really good look at one up close, I didnt want to reply with the wrong information.
Having found out, I can say that it will not "slide" onto the bottom of the grip frame as it does on the DM5. You will need some type of rail/drop to attach it.
I hope that this delay hasn't caused you to much inconvenience.
Jeff