Listed below are a few links that I have found for making BizTalk HL7 Accelerator performance configurations. This information is often very hard to find and I do not believe that Microsoft has any specific documentation on this topic. The first link is from BizTalk Hotrod magazine and it details the HL7 accelerator in depth. Look at page 60 for more details on performance configurations. The second link is from the Breeze Training blog. The configurations here are crucial for HL7 installations that have a high volume of messages.
BizTalk HotRod Article on the HL7 Accelerator
Registry Changes for increased message throughput
I will be posting in the future on some best practice configurations for hosts and host instances and general project setup.