Herman,
Having the bolt go through a slot instead of a round hole would allow the table to be lengthened or shortened as needed. (Total length would remain constant. The only change would be in the projected length toward the wheel.) Even if the final jig had just a hole (or a couple of holes for some adjustment), having a prototype with a slot would give a good feel for what projected length worked well.
Ken
Having the bolt go through a slot instead of a round hole would allow the table to be lengthened or shortened as needed. (Total length would remain constant. The only change would be in the projected length toward the wheel.) Even if the final jig had just a hole (or a couple of holes for some adjustment), having a prototype with a slot would give a good feel for what projected length worked well.
Ken