Replying to Ive used search bar, and cant find answer for this pvc question

so i have it all built except for the pvc to be attached.  now im debating over drill it in from the sides, but what if i want to do 270 on or something? the other option is drill it from the bottom, one thing is that i dont want it to crack and fall on screws, another is that how do you drill it so it gets the perfect spot on the rail for it to stay in place, instead of missing the pipe?