I’m adding windows to a “Tuff Shed” which is framed with 2×4’s and sided in T-111. I framed my rough opening and cut the T-111 about 1.5″ wider to allow access to screw the vinyl nail fin on all sides to my 2×4 framing. I’m planning to flash over the vinyl/screws with butyl tape and then install some 1″ t-111 strips as spacers, and then wood trim (19/32″ plywood trim) on top of that butted up to the window. The windows have a j-channel and the t-111 and trim together will fit inside it. I have read on various forums a recommendation NOT to caulk the joint between the trim and the j-channel because the channel is meant to have water in it. But my concern is, if water enters the channel at the top or sides, it would just drain down to the bottom and go back underneath the T-111 siding, obviously not good. So what is the recommended best practice for sealing wood trim to a vinyl j-channel like this?