Can see how it will come up out of the new position at the front of the door. To help it bend around the corners I found a carpenters pencil worked well. I secured the channel the same as stock with some small counter sink screws.
I cut some cardboard roughly into shape and then marked around the inside edge of the window channel. The added the depth of the channel, 10mm-3/8", to that mark with some dividers. Can see how it sits inside the channel. I made it go inside the door to add some stability to the front edge when down.
The bottom of the template is level with the top of the door card recess. I was happy to see that it cleared the door handle linkages. I will make templates from MDF next using the cardboard one to scribe around.
Bought a universal electric window kit. I went with the motor off around the side rather than fitted directly to the bottom of the guide rail to give me more mounting options. Before committing to cutting out my final window template, I wanted to make sure it went into the door deep enough. You need a minimum of 38mm-1.5" below the window sill to make sure it won't foul when the window is fully up. I made it 50mm-2" to give me a bit of room.
I thought the best place in height would be that the mounting bracket would sit directly over the ridge on the inner panel. Would be more strength there and the bolts heads would sit inside the ridge making them near flush so the door card would not bulge over them. Still enough room for the motor to be off the bottom of the door. The motor is normally faced toward the hinges.