We've chosen to not make Cal Kings. In order for us to make it, a Cal King latex block requires gluing an additional piece to the head or foot of a king size layer to get the additional 4" to get the proper length -- this is case for most latex since the longest molds are only 80". With regrets, we don't a glue system at our facility and don't have plans to install one at this time.
There a lot of good companies out there. They use quality materials and from what we hear, they stand behind their product and have good service, but I can't guarantee your experience since everyone is different.
Also, if you haven't already done so, we recommend checking out themattressunderground.com. It's a great resource for all things mattress and chances are you'll find helpful pointers there.