Phil, good question. I don't remember! Actually tonight I pulled the bracket off and removed the gear cover to re adjust the leadscrew - which had come loose and moved a bit. Only looked at the end of the slot, under the headstock. Never paid any attention to the rest of the ways. I'll look along the back of the ways tomorrow to be sure, but I vaguely remember the slot only going part way. A full length slot would be ideal for adding other attachments. Anchor point for one end of a tensioning bar for the countershaft for one. I'll check my lathe in the morning and update this post.
Glenn