Drilling the holes in the C-665 rear anchor blocks is one of the more challenging tasks during installation of the sliding canopy.
The process is quite easy but you will have to be very precise in measurements and drilling.

During this process, you drill a hole in the plastic block which is offset in angle in 2 directions. This makes the drilling quite complicated.

You start of by sliding the plastic block in the C-677 rear pin mount which should by now be drilled to the longeron and locked in position.
Then you slide forward the canopy until the pin of the canopy frame touches the plastic block.
Marke the exact location of this touch point on the black.

Then you drill a small hole in the block and fit and try it again.

The pin now penetrates the drilled shallow holes slightly.
Use a metal ruler to extend the line formed by the pin on the slider frame. That's the direction of insertion.

Now in the same way, use a metal ruler to draw the parallel line to the slider rail.
These two lines will define the angles at which to drill.

View from the front, you see the slider rail direction is nicely continued on the plastic block in the rear.

Now take the block to the bench drill press and use a vise to hold the block.
You want the line to be perpendicular (as the drill is also perpendicular. This guarantees the right direction for the going forward motion.

Next, you look in the other direction and the best is to use some spacing material on one end of the vise to lift it up until the drill is perpendicular again to the line on the block.

Check again in the other direction and verify the drill starts perfectly in the earlier drilled shallow point already present in the block.

Here's a shot of the entire setup. Notice the spacer on the left side under the vise which tilt to the correct angle for following the line formed by the slider rail.

Measure twice, and then drill just deept enough to accomodate the rear pin. I used painters tape to indicate the dept.

remove and test fit. this worked out very nice. It's a bit snug to open the slider and maybe I have to enlarge the hole slightly but I'm gonna leave it like this for now.

Same thing done on the passenger side. Frame pin fully inserted and butts against the block.