Seeking alternate methods of design

I design Vacuum forming tools that require a plug assist tohelp draw film down into cavites. The plugs need to have the sameshape as the cavities except the male radii on the plug will belarger and the plug needs to have a offset of anywhere from a 1/16"to 1/4" depending on the tool. The way I am currently doing this isin an assembly I create a new part and start offsetting thesurfaces of the cavity. Next I extend and trim the surfaces sothere are no gaps and knit into a solid. Then I apply all filletswhere I need them. On a simple part this takes a minute or two buton a complex part it can take an entire day. Can anyone give anyideas on alternate methods that would be faster?SolidworksParts And Features