I just call jottodesk directly and get the part numbers from them, then call the local rep and give him the part number. The people at the company are great, and very helpful. I tried to order through them the first time, and the company guy told me to order through my local rep to save money.
If you can tolerate a small , fine gap on the top or bottom, that would be the way to go.
The holes on the side are one long slot which will allow for adjustment of depth.
If you need a helpful rep there, ask for Keith, as he set me all up - heck, if need be, tell him to pull up Jonathon Whipple's order and see what mounts I used - there should be 2 of the same kind on my order - that would be the one!