Decisions and questions

I've decided to go with a set size of 4 X 6 inch. Since it's a matter of "having at least some beads" on it, I figured it would work well whether it was lightly or heavily beaded. One of my goals is going to be using things I already have with the fabric, bead, etc., trying not to buy extra unless there is an element of the piece that the piece absolutely needs that I don't already have. Sort of beading on a budget meets repurposing kind of thing.

I have some montage type picture frames that I never got around to putting photos in and thought they would work great for mounting my finished beaded pages in instead of shadow boxes that I would have to buy at some point. The only thing is, some of the slots go 4 X 6 and some go 6 X 4. I was wondering if I needed to keep the same orientation for every sheet of the project or if the direction I beaded was flexible as long as the finished size remained the same? Also, are those completely finished sizes or can I just use that as my maximum size and leave a half an inch box/frame around the edges for when I matte it for putting in the montage frame?

Edited to add: Ok, going with Susan's reminder in the comments I'm going to use fabric or backing at 4 X 6 and the actual beading will be 3 1/2 X 5 inch rectangles. I think that will give me plenty of room, but not so much it'll be overwhelming and leave me enough edge for framing. Got my January idea figured out this evening so off to play with the beads.