I am using the 5/16" spades on my Kharma loudspeakers with the same WBT ( with plastic slots ) and had no problem getting them to fit...Its a tight squeeze but managed to get them in..You could hand file off the spades sides slightly if neccassary or even open up the slots a bit if needed...Some people remove the WBT plastic housing completly ...Git er done.....Not that big if a deal,,