Proper way to Cap Windows with Siding already in place
I recently purchased a house that has aluminum siding, and I'd like to wrap the windows and doors. This is an investment property so it's not something I have to look at everyday, but I'd still like it to look nice and I'm pretty handy, so I will be doing this myself. (At least that's the plan...)
Most of the DIY videos I've watched online show the wrapping going up before the siding. In my situation, the siding is already up and I'm going to need to wrap over it. There are approx. 25 windows in this building and 5 doors, so it's going to be a lot of work, and removing the siding is not an option.
Attached is a cross-sectional view from the top showing what I'm working with. Capping the window sill and the top of the window looks pretty straight forward, but the sides are where I'm confused.
How should my capping and j-channel be attached to each other and where should the capping end? The two options I see are that either I cap completely around and over the j-channel, or I cut my cap flush with the front edge of the j-channel. If both of these are wrong, please let me know what you'd recommend.
Thanks in advance for your help.