we used straight 8s in some of ours this year. turned out fine. i've shied away from alum. some potential concerns. yet i continue to use my pit stick every day and i am pretty sure its in that. anywho... if you use alum, they say to use it to soak the cukes and not in the actual brine.
That would make sense. If I remember right, the lime works by Calcium diffusing into the cells in the cucumbers and giving them some structure after the heat damages the cells. I'd guess alum does something similar.