I built that particular motor for nitrous use with JE forged pistons, and the appropriate nitrous ring gap (~ 22-24 thousands if I recall correctly). I missed the part that you are running Hypers....supposedly "they" say you can get away with a small shot on hyperutectic pistons, but I have never ventured down that road....I'm not sure I would spray it with those pistons (I'm pretty conservative), but thats just me. Like any cast type piston, it can fracture when sprayed. If you must spray it , as Jpar said, pull more timing than needed and creep up on the tune. Maybe start at 28-30°...it will make it a bit of a dog running NA, but on the bottle it will make good steam.
For what its worth, my old 360 nitrous motor (in Colorado at Bandimere, 5800') would run ~13.8 NA and 11.0 on the bottle.
