Ottawa, ON
Quoted from Buckman:It's better to drill from the topside, what you'll find is that you'll most likely have a bit of a rough feeling once you drill the hole through (this would be on the bottom side of the ramp if you are drilling from the top). When the drill bit goes though it'll leave a bit of plastic on the hole that you just drilled through and what I would do is simply cut it off with a pair of small wire cutters.
You don't really want that on the top side, so I found it's easier to drill from the top. The pilot hole works out well when you drill from the bottom because you can get nice and close to the inside channel of the ramp, so that way all of your holes are nice and uniform all along the ramp. Using a small drill bit for a pilot hole also works out well because you'll find the larger drill bit will move around a little bit when you first start to drill it.
As for the drill bit size, just refer back to my thread with the video and you'll see I posted up a picture with an easy way to figure out what size drill bit will work work best.
Thanks! 
I got it now.
Lantana, TX
Udenhout
