As Socrates allready mentioned 
I made a masterpiece (wich I still have) and then casted a form
I can only suggest , take your time for cutting  , be patient , better cut five times a little bit then one time too much 
The corners in Gassy's medieval town were mine ,traded some stuff with him 
Those roofcorners were resincasts and immediately coloured 
Sadly the form got broken quickly and I didn't have time , money , and lust to make another mould yet