dont count on being able to run the hub right forward in the slot, as the disk mounts do go that far for some reason!
it would make sense for them to, so you can just throw the wheel in, but you cant, so tough.
Having said that, ive got a chain tug in there, and have no problems.
if your only going to use gears, you would buy a vertical, but im guessing your toying with SS and or Hub gear options, in which case, go for it.
only minor additional hastle.
also, the slotty has down tube cable and hose routing, and its a BB guide style cable guide.
up to you whether thats a good thing or not, ive got mine as a road bike, so its good i think.
if it was for off road, i would want full outers.