Adding SP modded maps to mainmenu.map, instead of replacing?

[benheadp2]

Does anyone know how (if it is possible) to add a modded SP level (such as The Epic Battle) to the 'mainmenu.map', so I don't have to disturb my regular campaign '03b_newmombasa.map'? Then i could just select it from the level select screen... did Bungie leave the SP campaign open enough to do that?

I tried adding it to the MP levels, but when i start the level all that shows up is lots of water...

does anyone want to write a nice little tut on how this is done... i promise, i'll keep trying and if i figure it out, i will write the tut and post it for all to glorify...