I have the PM-25. Handy little mill - still learning what it's limits are. Right now I have a 40 pound piece of A36 steel on the slab fly cutting 2.5" diameter with nice quite operation and great surface finish.
I had no issues with the nod (good front to back), but I needed to adjust the tilt of the head to tram (13 thousandths with an 8" swing on my DTI side to side).
I see people talk about the tramming aids, basically blocks they add to the side of the head to help precisely adjust the tilt.
I just slowly loosened the bolts a small bit at a time, and with a small soft piece of wood as a buffer and a brass hammer gently tapped the side until it started to move ever so slightly, took about 6 cycles of tapping and swinging the DTI to get it to read within .001" of each side - close enough that it won't really be the tram that induces the error but rather the lack of rigidity in the mill.
To keep that to a minimum - I am careful to keep my depth of cut on the low side of what should be possible and take it relatively slow. I guess the metal will tell you if it likes what you are doing.