I should have written this as soon as I got home from Hawaii. I was--and still am--delighted with my Spirit 2 mask (order #107719) that I received in May. I was leery of investing big bucks in custom ground optics because I don't do much diving anymore and I have a very strong prescription. However, I was going to Hawaii, and I do like to snorkel. So I invested in/gambled on your mask with stock lenses.
I was surprised how clear my vision was. I could see the grains of sand! I ended up snorkeling every day except for my travel days.
After many years of slightly fuzzy underwater vision, snorkeling with sharp vision was much more fun than my previous scuba and snorkeling trips.
If anyone is wondering if the higher diopter lenses work: Plugging my prescription into your calculator resulted in +3.5 and +4.0 lenses.