brainfart - "pushing" a smaller matrix into larger one

Hello, sorry for the lame question, but I've struggled long enough. I've tried scanwrap, repos, scanoffet, and just offset messages. I know this is simple, in fact I think I've done it before but?.

I just want to insert a matrix into another matrix pushing the data down the line. I can do this with lists, but do I really need to leave the matrix realm?

ie.

bang
|
V
jit.matrix 512 1
|
| (What goes here?)
V
jit.matrix 512 512

I want this data to go in at address 0,0. The rest of the matrix should scroll down to (0,1), what was at (0,1) before now goes to (0,2) etc. Lines that have not been filled should read 0. Data that falls off the end disappears.

Christopher Overstreet