|Sorry, I just got up. Here are my steps:
Cut length of sliders the length of the center of one kingpin to the other. The height is the distance of the plate to the center of the axel.
Cut top V cut. I would go 1/2" down for you. Mark center, 1/2" down, make a point, draw a line to each edge, cut.
Find how far the bottom can go to each side, make a mark, make a mark 3/4" from top, another one was 3/8" thickness for the bolt and extend inwards past the bolt. Cut out C shape but it will go up if you do the V on yours on top.
Place on plate, trim tops to make them triangular so they dont rub the trucks. WHen you can place them on your plates flush, trim outsides of tops of sliders to cut off the edge to make them more rounded. When all other cuts are dont, cut out center/bottom. I would give 3/4" on top and 1/2" or so on sides. Trim anything else as needed.
Place on plate, drill with a small drill holes. There isnt much room so I "ate" away to get the hole exact.
No, this is not an exact plan. But its how I work. I cut to fit, measure, adjust. Just think to go outside inwards. Otherwise you could end up with skinny sides.