Off the top of my head, and without changing much of the design.... adding full length top plates to which rest rafters on, I would cut the post top to the roof pitch, add a tenon and mortice the rafter for said tenon. Of note there is not much relish on top of the post for a tenon above the upper tie beam, consider adding a foot of post length to the post. (this will aid in adding to your brace lengths).
In addition, I would use a full length rafter on the long slope, no splice. The braces on the 2nd floor are too short. I see a mix of different length braces, to make your job of cutting easier I would standardize the brace length. You will appreciate this later.
The struts, indicated as J should bear on the foot of the king not the tie, roof load is transferred to the tie, you want to avoid this. (although the spans are small, in practice this is best). You could do away with the queens altogether, K and R.
