Charlie is spot on. The ring manufacturers recommendations are the minimum values. Tightening up on those recommendations is taking risks with ring end gaps that can butt together which in turn score the cylinder walls or break the piston lands. The old school of thought was for ring expansion on both rings being such that the ring gaps would be minimal without actually butting ends. Because the top ring runs hotter, it needs more required gap during the intial build than the cooler running second ring.
But the thought process on ring gaps has changed dramatically in the last twenty years. Because the top ring does the majority of the sealing and the 2nd ring is more for oil control, the second ring gap can be set as large or larger than the top ring gap. The thought process on this is for the second ring gap to be large enough to actually bleed off some of the pressure that occurs between the two compression rings which would otherwise unseat the rings at maximum pressure. This was originally validated through dyno testing by Sealed Power which showed that additional power is made by increasing the second ring gaps.
Along these same lines, some of the high performance pistons are available with an expansion groove between the two compression rings. This along with wider spaced rings allows additional room for ‘gas’ expansion and similarly prevents the rings from unseating due to pressure increases between the two compression rings.
Here’s a link to a past thread showing a picture of a Keith Black hypereutectic piston with the ‘expansion groove’ between the first and second rings.
http://www.y-blocksforever.com/forums/Topic9016-3-2.aspx
Lorena, Texas (South of Waco)