I'm just looking into making a few parts (in my usual sloooow pace) and I'm considering core materials.  I appreciate the convenience of soric however I'm looking for your opinions on ultimate weight minimisation.  I cant really use honeycombs as I have a single mould so please restrict it to common cores.  I'm looking for a comparison between thinks like soric, balsa, foam etc as to what is ultimately the lightest moulding.  I appreciate the extra labour with foam of infuse/bond/infuse but its just for myself.  My suspiscion is it will be foam, soric, balsa in order but I'm happy to be corrected.

Thanks y'all

Thanks for the reply.  I'm looking at car bodywork so some flat(ish) panels and some complex curves.  I can use a variety of core materials for the different sections.  The current panels are 3mm thick GRP (made by closed mould).  For some I can go thicker but for some areas I need to keep 3-4mm thickness. 

WRT the honeycombs I've just found things like nida plast which are pre-skinned.  I've never used them so would appreciate some input on if I can use them under vacuum (ie wet out outer skin, bond in core and then wet out inner skin).