We use plugs for petrophysical investigations. You did not tell us what kind of whole rock samples you take (sample spacing) and what sort of analysis are going to be done.

Your question will need more specification as to the core issue if you expect a near-tailor-made answer

HGD

An early exploration core should, ideally, be without a break. Things that might be missed in a 'one foot' gap include a thin volcanic tuff (for dating), or an unconformity etc. Spacing can increase with confidence and expectations.