My approach would be to plot it on a piece of paper. Using 1/4” graph paper always works good for me, along with a architects scaled ruler, and a pencil. You can figure it all out at your kitchen table using a scaled drawing.
Anyway, it is not required to use the manufacturers attic insulation shield. You can box it in with a chase. So, go ahead and place your 30* elbow as soon as you can, making sure you keep the 2” clearance to the ceiling joist. Use an offset support, and maybe even a roof support kit, under the flashing to stabilize the pipe after the offset. We find the roof support kit the best (this is a piece that bolts or straps to the pipe and has adjustable “wings” on it to allow you to place it on the pitched roof). It will be hard to keep the pipe plumb without it.
Sean