I didn't notice your question to me until now- sorry for the delay.
I don't own a BMBH. I was talking to Pan about another item I was ordering (down sleeves), and requested for him to sell me the poles. Soon afterwards, I noticed the availability of the poles on the BMBH page of their site.
The hammock I am currently making utilizes the BMBH pole at the head end only. I chose to go with 44" fabric width (before hemming). This will be the narrowest hammock I have made. However, I am working on a method of widening the middle of the hammock body. I am reattaching the pieces of fabric that I cut off from the lateral arcs. I reduce the depth of the curve by half on the pieces that I reattach. That way the side panels are not pulled overly tight when the hammock is hanging unnoccupied. Anyway, It is nearly completed, and I am pretty stoked about the results.
Now to answer your question: I don't know how wide the fabric is at the head end of the BMBH.