I was contemplating contributing but, first, they were already far past their target and, secondly and more importantly, I am unwiling to spend another $400 USD per hive on unproven technology. I am shooting for 100 hives in the near future (this year or next) so that would be $40,000 USD (or about $50,000 CDN). Plus shipping. That kind of money would buy an aweful lot of labour and conventional extraction equipment. Especially when there remain a lot of unanswered questions such as how will these frams fare from year to year and what kind of maintenance will be involved. Even to put down $400 bucks for an evaluation set is not very appetizing.
I think it is a very, very promising technology but I need a little more real life performance data before choosing to put out that kind of money. My hives complete with frames are costing me around $125-$150. So the FlowHives for me are a lot like looking at caviar and champagne for lunch.
Technically, they could be stacked but I think that, for commericall or semi-commercial apiary, the business case could would be hard to build. If someone were just keeping a couple of garden hives, it could all make sense.