You can do this one of two ways.
One, would be simple as what is called double jay.
Two, would be more costly, but would look better. This would be use Azek as a freeze board with jay top and bottom with z bend aluminum. Also this route you need two people pending on length of wall. Hope this...
As one that has put up countless boxes of siding. I have always used clear silicone on any piece of siding that is to small to fit into sill trim. To this day I or the company that I work for has yet to have a call back for any siding coming off or sliding down.
I have the m12 for a few years never let me down on my old dodge and trailer. only downside is if you don't use it enough and leave the tube in it without pulling the plunger back it inevitably leak out. Would I buy another, absolutely with the frequency that I use it for. Hope this help.
Using the staples on seat cushions on 3/4" ply and 3/4" flake board was very easy on the hands (repaired about a dozen chairs for a motel). I was even using either 5/16" or 1/2" staples and sank everyone right after getting the depth setting set right. I hope this will help you out a little bit.