OK Here goes.
As of the last beta of CompuShow I tested, the profile editor still did not allow for a fixture to have multiple R, G, or B slots. Therefor, you can patch a matrix with the full profile but the effects will only work for pixel 1. (Very few console manufacturers have this capability built in to their consoles as of yet.)
Build a Matrix of 3 Channel RGB Units. It can be handy to open a 3 channel LED fixture profile in the PROFILE EDITOR and name it Pixel and save it as Pixel.
Make a new page, Select your Pixel, and click Matrix. Here you put in not the amount of fixtures you have but the amount of PIXELS (RGB sets) and you ignore any other channels for the time being. Graph paper is highly advised.
MATRIX EDITOR can save a lot of time: I will demonstrate with the MegaPanel - the pixel layout will is the most frustrating:
1234
8765
26 Channel fixture, RGBRGBRGBRGBRGBRGBRGBRGBSI
In the advanced Matrix Options you can set the submatrix, what I just showed you, which will act as a unit that will follow whatever flow pattern you pick, those are the blue buttons with the arrows.
On the graph paper have a chart of all of your fixtures pixels lined up. Write in the starting DMX address of each pixel.
01 04 07 10 _ 27 30 33 36 _ 53 56 59 62
22 19 16 13 _ 48 45 42 39 _ 74 71 68 65
Have another chart that's a solid grid, your matrix, with the fixture numbers.
01 02 03 04 09 10 11 12 17 18 19 20
08 07 06 05 16 15 14 13 24 23 22 21
Now for the fun part... Open the page settings and go to the channel tab. The numbers you see will correspond to the matrix chart. Start with Pi1 (Pixel 1) Highlight it, One of the options is to change it's address, select this option and insert the address from the corresponding gridpoint on the DMX Chart.
Rinse and Repeat until you hate everything about computers and having to click Enter.
I hope this helps