Joist Pockets in Tie Beam

[Flavaflavin]

I am in the process of building a timberframed workshop. Im milling all spruce, 7" material. I've got a few bents put together but I'm trying to finalize my joinery on my tie beams. The 2nd floor will be living space, so live load but nothing heavy. The tie beam is a stout 7" x 12" spanning just 16'. Im planning on a larger central dovetailed joist (7" x 7") to connect each tie beam and then 5" x 7"s on 2' spacing. Right now I've got my tenons at 1 1/2" x 5 1/4", but that's looking like a lot of material out of my tie beam. The tenons will all fall above the neutral axis and should be in compression but I just feel funny about removing that much meat. How do others balance strength on the joist tenon vs removing material from the tie beam?