Ok, so i've made an era and I want to change the stock cps and health/ammo droids like Mav did in his Beach Troopers. I've changed the odfs and mshs in my common folder and munged, then moved the common.lvl in data_MAP\_LVL_PC to my map, but the droids stayed the same. After a clean and remunge I still got no change.

Am I going about this the wrong way or just forgeting something, req perhaps?

Use a custom ingame.lvl file loaded along side the stock one. The ODF and MSH files found in the subfolders of your data_***\Common folder are referenced in the ingame.req file, so doing what you did wouldn't work because the game would not be reading that common.lvl file. And plus, it doesn't contain those files you edited.

Ok, thanks AQT
I'll post the results.
Edit: It worked, sort of. I got the gonk droid replaced then changed the health droid and it crashed, working backwards.
Edit2
I had to make a new 3 letter map but now cps and droids are changed to my models.