New be question.. I am thinking of casting a MDF plug. It is a fuselage for a model airplane.. I have been looking on the net and other people have set the plug in a parting board. built up some sides to the parting board.. Then used a gel coat and then a epoxy mix to cast there mould's.. Do you have anything like this system. Or will the UNI mould making system do the same thing?  I cant see it being as ridged as a solid epoxy mould.. 

Cast moulds are a pretty old school, expensive way to go about it. Unimould is excellent, and is plenty rigid enough to make highly accurate moulds. Much easier to repair and restore if you ever need to as well.

You can also laminate moulds in much the same fashion as with Unimould, but using epoxy materials and woven fibreglass, for a slightly higher end mould. 

For what you are doing, I would recommend Unimould everyday of the week.