I went ahead and did this as follows, and it came out great. Will need to do a bit of sanding, but all in all it looks good:
– measure on the top side for the long cut (26 inches). draw a line the full length and then put a piece of tape across the line.
– flipped the board over and drew the long cut line on the bottom side of the bar top. cut with a circular saw.
– flipped back over to the top side and drew the cutout for the gutter (4inch and 4.5inches). did not tape this time.
– cut in on each end using a jigsaw
– cut the long line using a circular saw. ran a test cut in a scrap part of the gutter section of the top bar, measured to see how far back the blade would run when i dropped it in.
– marked the length of the blade for the drop-in in the long run, and then opened the guard and dropped the blade in paying attention to both the front and back sides of the blade to stay on the line.
– at each end, finish the cut w/ the jigsaw and free the cutout
seemed to work for me, but then again, i have no idea what i’m doing