Hi Bcgirl,
[quote]I am somewhat nervous about ordering online without trying it first but that is a very good value compared to want we have been looking at. I still would need to find out what mattress duties are for import but as it’s being made in the U.S., my guess there would be little to none.
Does this sounds like it has promise and would work for us? [/quote]
Mattresses.net is one of the members here and this would certainly be a good quality/value option. There would be no duty but of course there would be tax across the border and if you use a courier then there is normally a brokerage charge as well (but not if you bring it across yourself).
A manufacturer is generally the one that is most familiar with the specific options they have available and how well each one tends to “match” different body types and sleeping styles based on the averages of their customers that are similar to you so unless your own personal testing on similar mattresses indicates something different then their suggestions would usually have the highest odds of success. Having a split core is also a good way to accommodate different needs and preferences and in this case because the top layer is the same and the core is different the “feel” of the transition between the sides would be less than if the top layer was also split.
You certainly have some good quality/value options you are looking at (locally and online) and I’m looking forward to hearing about what you end up deciding and which one you decide is the best match for your personal value equation. 
Most of the pressure mapping systems are specific to a certain line of mattress and aren’t really relevant to mattresses as a whole which have different constructions. They also only measure surface pressure (which you can often feel in your own personal testing) but don’t provide input into alignment or how the pressure is distributed in the deeper body tissues or include the differences in physiology between people (pressure affects different people differently). There are a few more comments in post #2 here and post #4 here about pressure mapping systems.
They can be a useful tool for stores that have them available and where the results can translate into the specific mattress you are most interested in but they wouldn’t be the primary way I would make a purchase decision or be that useful if the mattress you are buying is different from the one you tested and the testing results can’t be easily “translated” into a mattress with a different design.
Phoenix