xtremeqg, you sir are a life saver. Here's the original cfg file. Note that it calls for the file extension of the model for some reason. "model = Squad/Parts/FuelTank/fuelTankSmall/mu" PART { name = TrippleTank module = Part author = UbioZurWeldingLtd rescaleFactor = 1 PhysicsSignificance = -1 node_stack_bottomfuelTankSmall0 = 0,-1.66575,0,0,0,0,1 node_stack_topfuelTankSmall2 = 0,1.66575,0,0,0,0,1 node_attach = 0.62625,0,0,0.125,0,0,1 CrewCapacity = 0 TechRequired = sandboxWeld entryCost = 0 cost = 675 category = Propulsion subcategory = 0 title = TrippleTank manufacturer = UbioZur Welding Ltd description = Warranty void during re-entry. attachRules = 1,1,1,1,0,0,0 mass = 0.375 dragModelType = default maximum_drag = 0.175 minimum_drag = 0.2625 angularDrag = 1.75 crashTolerance = 11.25 breakingForce = 93.75 breakingTorque = 93.75 maxTemp = 2900 fuelCrossFeed = True MODEL { model = Squad/Parts/FuelTank/fuelTankSmall/mu position = 0,-1.1105,0 scale = 1.25,1.25,1.25 rotation = 0,0,0 } MODEL { model = Squad/Parts/FuelTank/fuelTankSmall/mu position = 0,0,0 scale = 1.25,1.25,1.25 rotation = 0,0,0 } MODEL { model = Squad/Parts/FuelTank/fuelTankSmall/mu position = 0,1.1105,0 scale = 1.25,1.25,1.25 rotation = 0,0,0 } RESOURCE { name = LiquidFuel amount = 270 maxAmount = 270 } RESOURCE { name = Oxidizer amount = 330 maxAmount = 330 } } Here's the error log: Changed the offending portion of the code to the model name "model = Squad/Parts/FuelTank/fuelTankSmall/model" and Tada! It works now. Funny thing is that I suspected it was something like that when I looked at the cfg file. Didn't make sense to me why it was asking for the file extension and not the file name. At the time I changed it to the file name including the extension and nothing and I also changed it to the full path to the file and nothing. So even without looking at the debug log I suspected that was the problem, I just didn't give it the right solution. Don't know why I didn't look at the debug log before, I know better than that. Brain fart I guess. Anyway, it looks like the problem for Mac's might be the way it writes how it calls for the part in the cfg file and it's a matter of manually going in and fixing it for now. If I find that it continues to be an issue for parts after that then I'll report that so the developer can have a look when the time comes. Again thanks a ton for jogging the old noodle. Update: Just welded a few more things and that's the problem. Had to go into the cfg file and manually edit the model file for each part because it uses the .mu extension and not the file name. Very happy camper!