Ping the lines !

Crown, bow and wind, the organic indescrepencies responsible for 99% of all the joints that will not come togeather despite the seeming exactitude with which they were cut, are all easily overcome by describing those two perfect planes of reference through any timber, no matter how awful it is.

I grant you 3/16ths is not much, in a shed to be sheathed with boards, but throw that same crown into a plate the length NH is talking about to be put into a home to be enclosed with panels and you have a problem, you have telegraphed your crown to the surface of the structure. Harder to enclose with unfogiving materials and likely even percievable to the human eye.

Do a little expieriment for me, draw the section of your plate on a piece of paper full scale then draw two reference planes through that section at 1 1/2" from the reference faces, now draw the ascending and descending lines of your step lap rafter seats ( I don't recall but something tells me Jack's shed has these and angles are a perfect way to bring this home ) Finished ? Now draw a line 3/16ths above the theorectical surface of your stick and extend tha ascending/descending lines through it and you will see exactly how far your joinery is off.

That same drawing and those lines can be used to not just predict, but to know, ecactly where the entrance and exit wounds of your joinery should be, and the crown/bow/wind is canceled.

A perfect solution for our imperfect world.

Let the timber do what it want's and needs to do, put your joinery where it belongs !