Thanks, Rick. I'll try asking around on the SRGC forum.
I haven't had much trouble with using tap water for soaking seeds before. Surprising, really, since it's both very hard water and sometimes has a pH above 8.30.
I do have access to a lab with a Milli-Q water purification machine, so I'll see if using deionized water increases the germination success rate.
A 2-month warm, 2-month cold cycle might mimic the natural seasonal cycle better, but I am impatient.
Since I have a fairly large batch of seeds to work with (~300) I will try several methods just to see what works the best.