My understanding is from a few conversations with Don Snyder and Bill Stipe that Snyders is making the head...contracting the casting and machining. Bill Stipe did some combustion chamber design and testing work on the 6:1 head. I do not know who did the chamber design work on the 5.5:1 head.
I asked Don Snyder if he would cast 20 heads with a thicker lower shelf to allow Bill Stipe to custom machine the combustion chambers. I was looking for a combustion ratio of about 6.7:1 and the ability to go higher with in stock looking cast iron head. Bill was interested in the project but Don Snyder was not...the cores would have required some change and the cost may have been prohibitive. Not sure as to the specific reasons but Don's answer was not at this time.
Good Day
Dave in MN