Hello,
You won't find any LAN side MTU settings on any of the small business routers. The LAN ports are simply layer 2 switch ports, which means they will either forward or drop the larger packets. They have to be gigabit ports as well, Jumbo Frames do not work with anything less. Unfortunately I cannot find anything specific to this model, and I am unable to test it since I don't have any Jumbo capable NICs.
So your best bet is really to just give it a try. The switch ports on the router will either forward or drop the packets, and anyone going out to the internet will either lower their packet size using MTU discovery, or the router will fragment the packets down to a size appropriate for the WAN link.
I wish I could be more specific, but without being able to test it that is the most info I can give you right now.
Let me know how it goes,
Christopher Ebert