Like Brian and Skrews - just a matter of opinion based on individual experience.
IMO most forged pistons do not transfer the heat to the top ring as much as some hypereutectics do so unless you are planning to run it hard on a plate (meaning tuning the NO2 for max power) I don't feel there's that much of a risk of rings butting. The normal N/A gap would be .016-.018 on them. The ".004 per inch of bore" is a good fall back if you don't have a spec from the piston and/or ring manufacturer. So with Hastings adding another .004-.005" you've already got what you need. IMO, any "extra" gap on the top is detrimental to power.
On the larger 2nd ring gap - The top ring seals against the cylinder wall and the lower surface of the piston's ring land. The 2nd ring is not a compression sealing ring by design. It's an oil scraper. The theory is at higher rpms is the 2nd ring can trap gas pressure between it and the top ring, that pushes the top ring off the land and again, some ring seal is lost. So the thought is more gap on the 2nd means less possibility of the top ring being unseated.
