Ah, that's Chris. The number 9 looks like the "standard" allen adjustment, whereas the number 7 is a "corncob pipe" style adjuster. Depends on how you want to make the adjustment access really. I prefer allen purely because you can pop a tool holder onto the back of your headstock and keep em handy. I don't like Stewmac's hot rods because they require a DEEP trench which makes it hairy if you're making thin flat necks. Good job you're not buying a nuber 6 eh?
Sandpaper is cheap and easy to replace. A piece of glass isn't difficult to get ahold of either.
http://vfish.net/sharp.htm
Although instead of using spray adhesive, use wet and dry paper, wet it, wet the glass and "roll" it onto the glass. The paper should be stuck to the glass perfectly with no air/water bubbles. If you're pushing bubbles out, retry it. Flatten the "back" of the iron and then hone your bevel through the grits. Adding a marginal back bevel onto the iron helps keep it sharp apparently, although I have never tried this.
This isn't to say oilstones don't have their place of course, I just have never really used one due to me getting the results I need on my plane irons through this method instead.
By the way, those magnetic plane soles are awesome for those time when you might get forgetful and put your plane down sole-first. This can chip the blade. I hate grinding out chips and re-honing....