So Microsoft came back and said there are 3 things that have to be done and the values set will vary depending on each environment. Here is what we are testing. (You should consult Microsoft to get the values appropriate for your environmenmt.) I will post findings after testing.
Add the following keys to the msexchangedelivery.exe.config and edgetransport.exe.config:
<add key="RecipientThreadLimit" value="3"/>
<add key="MaxMailboxDeliveryPerMdbConnections" value="8"/>
You can choose values based on situation but RecipientThreadLimit should always be at least one fewer than MaxMailboxDeliveryPerMdbConnections.
On the journal hub transport servers:
set-MailboxTransportService -MaxConcurrentMailboxDeliveries 100
set-TransportService -MaxConcurrentMailboxDeliveries 100
After changing the values restart the Transport Delviery Service.