It seems like when an outgoing message is larger than what is specified via MSGTYPES, the BBS should not connect to the far end first before checking the size. Of course if there are other smaller messages in the queue, then the BBS needs to connect to the far end anyway.
I'm hoping the new feature will allow you to check the "Send new messages without waiting for poll timer" box in the settings for the TPRFN backbone sites, which will allow you to increase the standard forwarding timer.