if you gapped the top and second rings the same, the second ring gap will be larger in a running engine since it never see's the flame front and heat that the top ring will see.
another consideration is the material the rings are made of. different materials have different expansion rates. a top ductile iron ring is more dense than a cast iron second ring.
unless you have years of experience using all types of ring materials in varying applications to fall back on, your best bet is to follow the manufacturers recommendations regarding end gap. the only exception to that is when using the KB pistons it is imperative that you follow their top ring gap instructions instead.